No SBC. No FreeSWITCH. No rebuild.
After integrating enterprise telephony stacks the hard way for three years, we built the tool we always wished existed. sipsandwich is a self-service SIP switch that connects your existing PBX to Retell AI agents in minutes.
Full-stack voice AI
development
End to end, from prompt engineering to production telephony.
AI voice agent development
Custom LLM-powered phone agents on Retell AI. Inbound, outbound, and blended workflows built for enterprise reliability.
Telephony infrastructure
SIP trunking, PSTN connectivity, Jambonz deployments, Twilio and Telnyx integrations. Carrier-grade and built to scale.
CRM and platform integration
Deep integrations with Salesforce, HubSpot, GoHighLevel, and Zoho. Agents update records, book appointments, and sync data in real time.
Prompt engineering and QA
Systematic prompt development, conversation design, and QA testing that lifts call success rates.
White-label development
Build and deploy under your brand. We act as your technical team. NDA and white-label agreements available.
Automation workflows
Zapier, Make, and n8n pipelines that connect your voice agents to the rest of your stack.
AI calls powered
Real production deployments at scale, not demos. We have seen what breaks at volume and built systems for it.
In business since
We were automating telephony before voice AI was a category. That institutional knowledge is your edge.
Retell partner tier
The highest Retell AI designation. Only a handful of companies globally hold this status.
"Call Sandwich built our entire inbound AI agent stack. The CRM integration was seamless and the call quality exceeded our expectations from day one."
"Their Jambonz expertise saved us six figures in carrier costs. The migration was smooth and we now have full control over our telephony infrastructure."
"We tried two other vendors first. They understood Retell AI at a level nobody else could match. Our agent success rate went from 60% to 94%."
Ready to deploy at scale?
Whether it is your first AI agent or your millionth call, we have the infrastructure and the expertise to ship it.