We are not seeing a 30-second drop or missing ACK. Our SIP trace is: INVITE -> 100 Trying -> 200 OK -> ACK -> immediate BYE and caller hears “phone number not found.” Assistant ID exists and is valid. Please check Vapi-side ingress/org association + trunk credential/routing mode for our account (SIP Direct vs DID routing), and share the exact URI format we must send from Twilio.

Based on the documentation, the required SIP URI format for Twilio to Vapi is: sip:YOUR_PHONE_NUMBER@.sip.vapi.ai where: -

YOUR_PHONE_NUMBER

= your SIP number attached to the trunk -

<credential_id>

= your Vapi credential ID A "phone number not found" error can occur if the number is not registered or not associated with the correct credential in Vapi ([documentation](https://docs.vapi.ai/advanced/sip/twilio)). Could you please share the exact SIP URI you are sending from Twilio (with sensitive info redacted if needed)? This will help verify if the format and credential association are correct. Source: - [Twilio SIP Integration Documentation](https://docs.vapi.ai/advanced/sip/twilio)

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this shouldn’t be happening if the SIP handshake is clean like that. An immediate BYE right after ACK usually points to a routing or auth mismatch on the Vapi side (ingress mapping, org binding, or trunk mode). I can help you quickly verify: Vapi ingress ↔ org association SIP trunk credentials + routing mode (Direct vs DID) Exact Twilio URI format + headers required I’ve handled similar SIP/Twilio/Vapi issues before — happy to jump in and fix this fast @Devon

Hi, Could you please share the Call ID so we can look into this further? Thank you!