Transfer Call not working
I'm experiencing persistent transfer call failures and need technical assistance to identify the root cause. Despite following troubleshooting steps, transfers continue to fail at the platform level.
Issue Summary:
Transfer function executes successfully ("Transfer initiated" in logs)
All calls end with "call.in-progress.error-transfer-failed"
No outbound calls appear in Twilio console logs
Problem occurs consistently across multiple test calls
Configuration Details:
Using Twilio phone number as SIP provider
Transfer destination: +15625002833
SIP REFER enabled on Twilio trunk (per previous support guidance)
Function configured correctly with proper destination parameter
Call Logs Attached:
Call ID: 6fe32c43-2e1f-4aff-a0d2-3c6e64f372ea (latest failure)
Call ID: 69a35442-1cce-4da7-a68d-5524d96fcf79 (previous failure)
Call ID: bbf10970-ec01-4ef6-8729-809121c6c84e (earlier failure)
What I've Already Tried:
Verified phone number format (+15625002833)
Confirmed function parameters are correct
Enabled SIP REFER on Twilio trunk
Tested with multiple different call attempts
What I Need:
The current logs don't show SIP-level details. I need you to investigate:
Are SIP REFER messages actually being sent to Twilio?
What specific error response is Twilio returning?
Is there a Vapi-Twilio integration issue causing the failures?
The transfers fail after your platform reports "Transfer initiated," but before any call reaches Twilio. This suggests the issue is within Vapi's transfer processing, not the destination number or Twilio configuration.
Please provide SIP-level debugging information or escalate to your engineering team for deeper investigation.
Account Details:
Org ID: 163cbd95-9a5b-48a2-b004-3728a6a4ae46
Using Twilio as telephony provider
Thank you for your assistance.
Issue Summary:
Transfer function executes successfully ("Transfer initiated" in logs)
All calls end with "call.in-progress.error-transfer-failed"
No outbound calls appear in Twilio console logs
Problem occurs consistently across multiple test calls
Configuration Details:
Using Twilio phone number as SIP provider
Transfer destination: +15625002833
SIP REFER enabled on Twilio trunk (per previous support guidance)
Function configured correctly with proper destination parameter
Call Logs Attached:
Call ID: 6fe32c43-2e1f-4aff-a0d2-3c6e64f372ea (latest failure)
Call ID: 69a35442-1cce-4da7-a68d-5524d96fcf79 (previous failure)
Call ID: bbf10970-ec01-4ef6-8729-809121c6c84e (earlier failure)
What I've Already Tried:
Verified phone number format (+15625002833)
Confirmed function parameters are correct
Enabled SIP REFER on Twilio trunk
Tested with multiple different call attempts
What I Need:
The current logs don't show SIP-level details. I need you to investigate:
Are SIP REFER messages actually being sent to Twilio?
What specific error response is Twilio returning?
Is there a Vapi-Twilio integration issue causing the failures?
The transfers fail after your platform reports "Transfer initiated," but before any call reaches Twilio. This suggests the issue is within Vapi's transfer processing, not the destination number or Twilio configuration.
Please provide SIP-level debugging information or escalate to your engineering team for deeper investigation.
Account Details:
Org ID: 163cbd95-9a5b-48a2-b004-3728a6a4ae46
Using Twilio as telephony provider
Thank you for your assistance.
