# Whistle

> Whistle is a global B2B sales development agency that provides outsourced SDR services and vetted SDR talent to help startups and scale-ups build predictable sales pipeline. Whistle runs multi-channel outreach across phone, email and LinkedIn, along with the supporting technology, data and analytics, so client sales teams can focus on closing revenue.

Whistle was founded in 2020 by brothers David Zeff (CEO) and Yonah Zeff (COO), following three tech exits spanning a decade in SaaS sales. The company is fully remote, merit-led, and made up of a team of over 100 people across Management, Operations, Data Research, Content Marketing, Sales and Sales Development, supporting clients in every time zone. Whistle offers two core engagement models: a fully managed Outsourced SDR department that goes live within 10 business days, and a Hire SDRs model that places vetted sales development representatives so clients can start booking meetings within 5 days. Whistle books qualified meetings and generates pipeline; the client's sales team closes the revenue.

## Key Facts

- Global B2B sales development agency, founded 2020, fully remote.
- Led by David Zeff (CEO) and Yonah Zeff (COO).
- Team of over 100 people supporting clients in every time zone.
- Trusted by over 350 companies.
- Generated $100M+ in opportunities for clients to date.
- Whistle clients have raised over $2Bn in funding and generate over $16.67M per month in pipeline sourced from Whistle's SDRs.
- HubSpot partner. GDPR compliant.
- Contact lines: USA +1 (628) 300-0991, Israel +97 233720098, Australia +61 258500042.

## How Whistle Works

- Two service models: a fully managed Outsourced SDR department (live within 10 business days) and Hire SDRs (vetted reps, meetings within 5 days).
- Multi-channel outreach across cold calling, cold email and LinkedIn, with messaging and multi-step sequences built per campaign.
- Each engagement includes a dedicated Account Manager and Team Leader who coach SDRs, monitor activity and deliver weekly deep-dive reports.
- Access to WhistleOS, an in-house operating system and toolset for outreach built on years of testing.
- Validated prospect lists built from major databases and AI tools, based on the client's ICP.
- Live reporting with insights by geography, job title, industry, company size, channel and list, delivered on daily, weekly, monthly and quarterly cadences.
- A proven multi-step process refined across more than 300 companies.

## Core Values

- We win together: collaborative groups working toward a common vision, prioritising winning together over individual credit.
- We work with people we like and trust: an environment of trust, transparency, support, respect, happiness and growth, for clients and team alike.
- We look for the simplest solution first: the least resource-demanding solution to the problem at hand.
- We own our desk: individual responsibility for success, growth, failures and learnings.
- We have each other's backs: clients are treated with respect, and in conflict the team takes precedence.
- We have a growth mindset: no skill or task is beyond reach; results are a function of time, resources and effort.
- We enjoy what we do: happiness improves performance and is contagious.

## Leadership Team

- David Zeff: CEO and co-founder.
- Yonah Zeff: COO and co-founder.
- Cheryl Segon: Head of Finance.
- Bronwyn Johnson: Head of Customer Success.
- Kayla du Plessis: Head of GTM.
- Bianca Goodrich: Head of Human Resources.

## Core Services

- [Outsourced SDR](https://www.whistle.ltd/outsourced-sdr): Fully managed SDR team with done-for-you pipeline generation, live within 10 business days. Clients choose team size and scale up as needed, with a dedicated Account Manager, Team Leader and content team running strategy, outreach, sequencing and reporting.
- [Hire SDRs](https://www.whistle.ltd/hire-sdrs): Hire vetted SDRs, with an average of 5+ years of experience, and start booking meetings within 5 days, without spending weeks interviewing unqualified candidates.

## Supporting Services

- [Cold Calling Services](https://www.whistle.ltd/cold-calling-services): SDRs use the phone to build trust and book qualified meetings.
- [Cold Email Outreach](https://www.whistle.ltd/cold-email-outreach): High-performing email campaigns that spark real conversations which convert.
- [LinkedIn Outreach](https://www.whistle.ltd/linkedin-outreach): Personalised LinkedIn outreach that earns replies and strengthens your network.
- [Pipeline Generation](https://www.whistle.ltd/pipeline-generation): A steady stream of qualified leads through outbound sales development so your team can focus on closing.
- [RevOps for HubSpot](https://www.whistle.ltd/revops-for-hubspot): CRM maintenance and process automation to help Sales and Marketing move faster.
- [Data on Demand](https://www.whistle.ltd/data-on-demand): Accurate, verified leads so outbound never stalls because of bad data.
- [Conference Lead Generation](https://www.whistle.ltd/conference-lead-generation): Lead generation focused on conferences and events.

## Solutions by Industry

- [SaaS & AI](https://www.whistle.ltd/saas-ai): Outsourced SDR and lead generation for SaaS and AI companies.
- [Cyber Security](https://www.whistle.ltd/cyber-security): Outsourced SDR and lead generation for cyber security companies.
- [Finance](https://www.whistle.ltd/finance): Outsourced SDR and lead generation for finance companies.
- [Marketing](https://www.whistle.ltd/marketing): Outsourced SDR and lead generation for marketing companies.
- [Education](https://www.whistle.ltd/edtech): Outsourced SDR and lead generation for education and EdTech companies.
- [Healthcare](https://www.whistle.ltd/healthcare): Outsourced SDR and lead generation for healthcare and health tech companies.
- [HR & Workforce](https://www.whistle.ltd/human-resources): Outsourced SDR and lead generation for HR tech and workforce companies.
- [Real Estate](https://www.whistle.ltd/real-estate): Outsourced SDR and lead generation for real estate companies.

## Solutions by Company Stage

- [Enterprise](https://www.whistle.ltd/enterprise): Sales development solutions for enterprise organisations.
- [Growth](https://www.whistle.ltd/growth): Sales development solutions for growth-stage companies.
- [Early Stage](https://www.whistle.ltd/early-stage): Sales development for early-stage startups, launching in 10 days rather than 6 months.

## Case Studies: SaaS & AI

- [vcita](https://www.whistle.ltd/case-studies/vcita): High-performing SDR team for vcita's US market. $11.4M pipeline, 89X ROI.
- [Powtoon](https://www.whistle.ltd/case-studies/powtoon): Converting freemium users to enterprise power-users. $8M pipeline, 19X ROI.
- [Rezdy](https://www.whistle.ltd/case-studies/rezdy): Reanimating cold leads with a multichannel outbound engine. $6.6M pipeline, 53X ROI.
- [Pecan](https://www.whistle.ltd/case-studies/pecan): High-performing outbound engine. $5.7M pipeline, 26X ROI.
- [UserWay](https://www.whistle.ltd/case-studies/userway): Web accessibility, from PLG free trials to enterprise. $3.6M pipeline, 23X ROI.
- [SecondNature](https://www.whistle.ltd/case-studies/secondnature): First outbound motion for AI-driven sales training. $3.4M pipeline, 22X ROI.
- [Ministry Brands](https://www.whistle.ltd/case-studies/ministrybrands): New markets in church fundraising tech. $2.7M pipeline, 24X ROI.
- [Lodestar](https://www.whistle.ltd/case-studies/lodestar): Structuring sustainable pipeline growth. $2.6M pipeline, 22X ROI.
- [Cloud-Based Connectivity](https://www.whistle.ltd/case-studies/cloud-based-connectivity): Scaling qualified lead conversion. $2.3M pipeline, 39X ROI.
- [Loops](https://www.whistle.ltd/case-studies/loops): Scalable outbound engine for a founder-led startup. $1.8M pipeline, 30X ROI.
- [Setpoint](https://www.whistle.ltd/case-studies/setpoint): Climate control sales and infrastructure. $1.8M pipeline, 14X ROI.
- [Solpod](https://www.whistle.ltd/case-studies/solpod): Solar-as-a-service, re-deployable outbound motion in Australia. $1.8M pipeline, 30X ROI.
- [Atlan](https://www.whistle.ltd/case-studies/atlan): Global pipeline for AI-ready metadata governance. $1.5M pipeline, 13X ROI.
- [NextNRG](https://www.whistle.ltd/case-studies/nextnrg): Repeatable sales engine via cold storage outreach. $1.3M pipeline, 40X ROI.
- [RingCentral](https://www.whistle.ltd/case-studies/ringcentral): Net-new meetings through a pay-per-meeting model. $1.3M pipeline, 14X ROI.
- [Zendesk](https://www.whistle.ltd/case-studies/zendesk): Partner pipeline for global expansion. $850K pipeline, 15X ROI.
- [Albi](https://www.whistle.ltd/case-studies/albi): Outbound sales for a restoration management platform. $820K pipeline, 11X ROI.
- [R-Go Robotics](https://www.whistle.ltd/case-studies/r-go-robotics): Securing $1M+ robotics deals with outbound SDR support. $820K pipeline, 25X ROI.
- [Exelera](https://www.whistle.ltd/case-studies/exelera): Outbound lead generation for a digital infrastructure provider. $720K pipeline, 40X ROI.
- [Control Monkey](https://www.whistle.ltd/case-studies/control-monkey): Technical sales from founder-led to SDR-driven. $640K pipeline, 17X ROI.
- [GreenRoad](https://www.whistle.ltd/case-studies/greenroad): Geo-targeting to transform the sales pipeline. $605K pipeline, 10X ROI.
- [Varada](https://www.whistle.ltd/case-studies/varada-inc): Big data queries and enterprise acquisitions. $550K pipeline, 79X ROI.
- [AI-Work](https://www.whistle.ltd/case-studies/ai-work): Event outreach and managed SDR services. $525K pipeline, 20X ROI.
- [Journey](https://www.whistle.ltd/case-studies/journey): Beta user acquisition for a CEO platform via LinkedIn. $440K pipeline, 17X ROI.
- [Programa](https://www.whistle.ltd/case-studies/programa): Dual-sided supplier marketplace in Australia. $360K pipeline, 20X ROI.
- [Obee](https://www.whistle.ltd/case-studies/obee): Proactive outbound sales for hospitality tech. $340K pipeline, 11X ROI.
- [RedFlag](https://www.whistle.ltd/case-studies/redflag): High-intent pipeline via consultative outbound. $250K pipeline, 5X ROI.
- [Revuze](https://www.whistle.ltd/case-studies/revuze): Inbound reliance to a data-driven mixed motion. $200K pipeline, 11X ROI.
- [Super Legal](https://www.whistle.ltd/case-studies/super-legal): US legal presence with AI-driven contract review. $180K pipeline, 9X ROI.
- [Lusha](https://www.whistle.ltd/case-studies/lusha): Expanding reach and reducing CAC. $177K pipeline, 195X ROI.
- [SayWhatt](https://www.whistle.ltd/case-studies/saywhatt): Structured lead generation engine to scale demo volume. $135K pipeline, 8X ROI.
- [Go-Crisp](https://www.whistle.ltd/case-studies/go-crisp): CPG growth via event and multi-channel outreach. $125K pipeline, 2X ROI.
- [WNSTN](https://www.whistle.ltd/case-studies/wnstn): OCR and technical superiority to secure pipeline. $100K pipeline, 7X ROI.
- [EverX](https://www.whistle.ltd/case-studies/everx): Outreach with precision and personalisation. $18K pipeline, 100X ROI.
- [Unity](https://www.whistle.ltd/case-studies/unity): Multi-channel outreach for event-driven pipeline.
- [Cue](https://www.whistle.ltd/case-studies/cue): Automating revenue reporting and CRM hygiene.
- [Digital Accessibility Leader](https://www.whistle.ltd/case-studies/digital-accessibility-leader): Converting free users into paying customers.

## Case Studies: Cyber Security

- [BlinkOps](https://www.whistle.ltd/case-studies/blinkops): Scaling top-of-funnel opportunities with tailored SDR services. $6.4M pipeline, 40X ROI.
- [Argus Cyber Security](https://www.whistle.ltd/case-studies/argus-cyber-security): Improving inbound lead conversion. $5M pipeline, 41X ROI.
- [OneLayer](https://www.whistle.ltd/case-studies/onelayer): Event registrations via a dual-goal survey and outreach strategy. $3.5M pipeline, 40X ROI.
- [DigiCert](https://www.whistle.ltd/case-studies/digicert): Refining outbound messaging to unlock pipeline. $700K pipeline, 44X ROI.
- [Click Armor](https://www.whistle.ltd/case-studies/clickarmor): Strengthening security awareness. $225K pipeline, 12X ROI.
- [AironWorks](https://www.whistle.ltd/case-studies/aironworks): Brand awareness and pipeline growth. $160K pipeline, 17X ROI.
- [N2WS](https://www.whistle.ltd/case-studies/n2ws): Improving inbound lead qualification and meeting conversion. 57X ROI.

## Case Studies: Finance

- [GK8 (a Galaxy company)](https://www.whistle.ltd/case-studies/gk8): Accelerating pipeline conversion. $17.25M pipeline, 170X ROI.
- [FinTech Software Leader](https://www.whistle.ltd/case-studies/fintech-software-leader): Scaling global sales. $4M pipeline, 57X ROI.
- [E-Commerce Company](https://www.whistle.ltd/case-studies/ecommerce-company): Building a scalable SDR function. $600K pipeline, 11X ROI.
- [Sharetec](https://www.whistle.ltd/case-studies/sharetec): Building a structured outbound engine. $510K pipeline, 10X ROI.
- [Tax Systems](https://www.whistle.ltd/case-studies/tax-systems): Accelerating GTM for Pillar 2 compliance. $325K pipeline, 7X ROI.
- [Venture Capital](https://www.whistle.ltd/case-studies/venture-capital): Turning inbound leads into investor meetings. $270K pipeline, 15X ROI.
- [Topograph](https://www.whistle.ltd/case-studies/topograph): Doubling first-month meeting goals. $150K pipeline, 6X ROI.
- [Park Road Advisors](https://www.whistle.ltd/case-studies/park-road-advisors): Scaling LinkedIn outreach. $150K pipeline, 17X ROI.

## Case Studies: Marketing

- [Shell](https://www.whistle.ltd/case-studies/shell): Refining fleet data and targeting for fuel card outreach. $32M pipeline, 186X ROI.
- [Mayple](https://www.whistle.ltd/case-studies/mayple): Scalable SDR function for rapid growth. $6.6M pipeline, 16X ROI.
- [Kaltura](https://www.whistle.ltd/case-studies/kaltura): Generating consistent sales qualified leads. $5M pipeline, 16X ROI.
- [Ticketing Platform](https://www.whistle.ltd/case-studies/ticketing-platform): Driving competitive wins for a leading ticketing platform. $3.9M pipeline, 27X ROI.
- [Splendid Group](https://www.whistle.ltd/case-studies/splendid-group): Specialised SDR talent for agile B2B campaigns. $1.6M pipeline, 11X ROI.
- [Deepdub](https://www.whistle.ltd/case-studies/deepdub): Predictable outbound engine for AI-powered localisation. $1.5M pipeline, 67X ROI.
- [Brew](https://www.whistle.ltd/case-studies/brew): Optimising outreach and rescuing ROI amid downsizing. $516K pipeline, 11X ROI.
- [Brand Chemistry](https://www.whistle.ltd/case-studies/brandchemistry): Building a systematic outbound engine. $465K pipeline, 14X ROI.
- [AudienceLed](https://www.whistle.ltd/case-studies/audienceled): Scaling B2B demand through strategic outbound. $360K pipeline.
- [Bambassadors](https://www.whistle.ltd/case-studies/bambassadors): Brand visibility through creator and Meta partnerships. $260K pipeline, 11X ROI.
- [Bound Marketing](https://www.whistle.ltd/case-studies/bound-marketing): Optimising HubSpot to drive predictable revenue. $120K pipeline, 8X ROI.
- [Biteable](https://www.whistle.ltd/case-studies/biteable): Validating enterprise sales and accelerating product insights. $106K pipeline, $74K ROI.
- [Sinorbis](https://www.whistle.ltd/case-studies/sinorbis): Building a high-velocity US sales pipeline. $184K pipeline, 2X ROI.
- [RedK](https://www.whistle.ltd/case-studies/redk): Laying the foundation for scalable CRM success. $16K pipeline, 2X ROI.

## Case Studies: Education

- [Verbit](https://www.whistle.ltd/case-studies/verbit): Market expansion with scalable outbound outreach. $1.94M pipeline, 13X ROI.
- [Panna](https://www.whistle.ltd/case-studies/panna): Rapid business growth and scalability. $1.2M pipeline, 3X ROI.
- [Clipboard](https://www.whistle.ltd/case-studies/clipboard): APAC growth story with scaled outbound. $620K pipeline, 14X ROI.
- [LivedX](https://www.whistle.ltd/case-studies/livedx): Outbound strategies for a new EdTech concept. $620K pipeline, 13X ROI.
- [FuelEd](https://www.whistle.ltd/case-studies/fuel-ed): Optimising outbound sales and pipeline operations. $520K pipeline, 11X ROI.
- [PocketPrep](https://www.whistle.ltd/case-studies/pocketprep): Scaling outbound sales with dedicated SDR support. $305K pipeline, 4X ROI.
- [Thinkific](https://www.whistle.ltd/case-studies/thinkific): A smart outbound engine to diversify GTM and drive enterprise pipeline. $150K pipeline, 4X ROI.
- [Veeya](https://www.whistle.ltd/case-studies/veeya): Outbound engagement for K-12 and non-profit IT services. $135K pipeline, 13X ROI.

## Case Studies: Healthcare

- [Sensi.AI](https://www.whistle.ltd/case-studies/sensi-ai): Building a professional sales function and outbound engine for health tech. $2.7M pipeline, 7X ROI.
- [Exclugo](https://www.whistle.ltd/case-studies/exclugo): Strengthening healthcare pipeline through targeted SDR campaigns. $540K pipeline, 10X ROI.
- [Kara Water](https://www.whistle.ltd/case-studies/karawater): Scaling investor outreach via targeted phone campaigns. $330K pipeline, 22X ROI.
- [Century](https://www.whistle.ltd/case-studies/century): Introducing scalable outbound sales processes in long-term care. $197K pipeline, 3X ROI.
- [BioBeat](https://www.whistle.ltd/case-studies/biobeat): Transforming a fragmented market into a data-driven sales engine.

## Case Studies: HR & Workforce

- [Dot Compliance](https://www.whistle.ltd/case-studies/dot-compliance): Scaling global pipeline. $7.7M pipeline, 8X ROI.
- [Parita](https://www.whistle.ltd/case-studies/parita): Scaling HR outreach with multi-channel SDR campaigns. $2.5M pipeline, 46X ROI.
- [myInterview](https://www.whistle.ltd/case-studies/myinterview): Scaling AI-powered talent acquisition with SDR outreach. $1.2M pipeline, 37X ROI.
- [MoleMap](https://www.whistle.ltd/case-studies/molemap): Expanding reach through strategic lead generation. $903K pipeline, $220K ROI.
- [Anywell](https://www.whistle.ltd/case-studies/anywell): Strategic meetings for on-demand workspace solutions. $820K pipeline, 15X ROI.
- [Elvee](https://www.whistle.ltd/case-studies/elvee): Optimising prospect engagement and sales operations. $250K pipeline, 6X ROI.
- [Black Professionals in Tech Network](https://www.whistle.ltd/case-studies/bptn): Streamlining lead generation. $230K pipeline, 5X ROI.
- [CheckProof](https://www.whistle.ltd/case-studies/checkproof): Bridging the SDR gap in heavy industry. $150K pipeline, 4X ROI.
- [WiseStamp](https://www.whistle.ltd/case-studies/wisestamp): Converting trial leads into qualified sales opportunities. $117K pipeline.
- [Speakap](https://www.whistle.ltd/case-studies/speakap): Fueling US market expansion through a performance-based sales engine. $100K pipeline, 10X ROI.
- [AskYourTeam](https://www.whistle.ltd/case-studies/the-future-of-remote-work): Strategic campaign success. $96K pipeline, 40X ROI.

## Case Studies: Real Estate

- [PropTech Innovator](https://www.whistle.ltd/case-studies/proptech-company): Building sales operations from the ground up. $15.45M pipeline, 23X ROI.
- [ClearCalcs](https://www.whistle.ltd/case-studies/clearcalcs): Scaling lead management with dedicated SDR support. $4.3M pipeline, 53X ROI.
- [Blok](https://www.whistle.ltd/case-studies/blok): Turning limited leads into SQLs with targeted outreach. $400K pipeline, 18X ROI.
- [Wander](https://www.whistle.ltd/case-studies/wander): Driving lead engagement and revenue growth. $312K pipeline, 5X ROI.
- [SiteScout360](https://www.whistle.ltd/case-studies/sitescout360): Navigating the off-site challenge. $168K pipeline, 5X ROI.

## Resources

- [Blog](https://www.whistle.ltd/blog): Articles on outbound sales, SDR outsourcing, lead generation and sales development.
- [Our Experts](https://www.whistle.ltd/our-experts): The people behind Whistle's sales development programs.
- [Guide to Outsourced SDR Services](https://www.whistle.ltd/post/guide-to-outsourced-sdr-services): What SDR outsourcing means, how engagements work, and when it fits.
- [Best Outsourced SDR Providers](https://www.whistle.ltd/post/best-outsourced-sdr-providers): Comparison of top sales development outsourcing companies.
- [Best Outsourced SDR Agencies in 2026](https://www.whistle.ltd/post/best-outsourced-sdr-agencies-in-2026): Profiles of leading outsourced SDR agencies for 2026.
- [Outsourced Sales Development for 2025 Growth](https://www.whistle.ltd/post/outsourced-sales-development-2025): The case for outsourced sales development and its benefits.

## Free Tools

- [Lead Projection Calculator](https://www.whistle.ltd/lead-projection-calculator): Benchmark lead conversion rates drawn from over 300 companies.
- [EduConnect App](https://www.whistle.ltd/educonnect): Free tool for education and EdTech lead generation.
- [Conference Finder Tool](https://whistle-conference-finder-tool.base44.app/): Tool for finding relevant conferences and events.
- [Free Cold Calling Scripts](https://www.whistle.ltd/cold-calling-scripts): Downloadable cold calling scripts.

## Company

- [About Us](https://www.whistle.ltd/about): Background on Whistle, its founders, team and values.
- [Careers](https://www.whistle.ltd/careers): Open roles and careers at Whistle.
- [Book a Meeting](https://www.whistle.ltd/book-a-meeting): Book a free strategy call with the Whistle team.

## Optional

- [Case Studies (full library)](https://www.whistle.ltd/case-study): The complete, filterable set of Whistle client case studies by industry.
- [Outsourced SDR Services in London](https://www.whistle.ltd/outsourced-sdr-services-in-london): Outsourced SDR services page for the London market.
- [B2B Lead Generation for EdTech](https://www.whistle.ltd/b2b-lead-generation-for-edtech-training): Lead generation page for EdTech and training companies.
- [Terms and Conditions](https://www.whistle.ltd/terms-and-conditions): Website terms and conditions.
- [Privacy Policy](https://www.whistle.ltd/privacy-policy-page): Privacy policy and data handling.