To integrate Vapi as your main receptionist without relying on intermediaries like Twilio, you'll need to migrate from RingCentral to a more open SIP-based telephony provider or a self-hosted PBX solution like Asterisk or FreeSWITCH. This setup allows direct SIP call routing to Vapi, enabling full control over call flow and AI handling. RingCentral’s closed architecture does not support direct SIP integration with third-party AI systems like Vapi.