RyGuy
11/02/2025, 10:56 PMChiranjeet Mishra
11/02/2025, 10:56 PMRyGuy
11/02/2025, 11:35 PMChiranjeet Mishra
11/04/2025, 6:45 PMendedReason in the API response ([reference](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops)).
2. Configuration Check:
- Ensure serverMessages in your Vapi configuration does not include "phone-call-control", unless implementing custom transfer logic.
- Set phoneCallProviderBypassEnabled to false for standard Vapi-managed call transfers.
3. Analyze Telephony Provider Logs:
- Use the phoneCallProviderId to search call logs in your telephony provider's dashboard (e.g., Twilio, Vonage, Telnyx).
- Look for errors related to the transfer.
4. For SIP Calls:
- Download and examine the SIP packet capture using tools like Wireshark.
- Check for REFER packets to ensure the transfer request was sent ([see guide](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops)).
5. Common Solutions:
- Ensure the destination number format includes the country code.
- Test calling the destination directly.
- Consider any call blocking features that may interfere.
By following these steps, you should be able to identify and resolve any underlying issues causing call drops during forwarding.