Telephony and BYOC Support in Retell vs Vapi: Connecting Phone Numbers to Voice Agents

Comparing how Retell AI and Vapi handle telephony — SIP trunking, PSTN integration, BYOC (bring your own carrier), and what it takes to port or connect a phone number — is a practical question that depends on each platform's documented capabilities. This article cannot answer it: the facts available do not cover Retell AI, Vapi, SIP trunking, PSTN integration, BYOC, or phone number porting for either platform. The provided source material concerns two unrelated studies hosted on arXiv — one on AI predictions and human decision-making behavior, and one on OpenAI's public discourse around ethics and safety. Neither addresses voice agent telephony infrastructure. If you have documentation or specs for Retell AI and Vapi's telephony features, providing those would allow the comparison to be written.