I'm using the VAPI UI (phone numbers). I have valid Vonage credentials in my Integration. Fail outbound calls At first, I've been trying to sync phone numbers with Vonage accounts, and that succeeded. I could sync and see my vonage numbers in my VAPI UI. However, outbound calls (sent via the UI) would not go through - see attached screenshot. Example call id : 019a07df-afb2-7aac-9fd5-ba02c600acd8 Failed phone sync I've tried multiple things on Vonage and VAPI side. One of them has been to delete my phone number on vapi side, then try again. And now this doesn't work either ! While it worked earlier. {"message":"Couldn't Update Vonage Number. Error: Request failed with status code 420","error":"Bad Request","statusCode":400}

Thank you for sharing the error details and call ID. To help diagnose the "call.start.error-get-transport" and sync issues, could you confirm if your Vonage phone number still appears as "active" in both the Vapi UI and your Vonage dashboard, or do you see any additional error messages or status changes there? Source: - [Call ended reasons](https://docs.vapi.ai/calls/call-ended-reason)

Knowing where the issue comes from : making a new ticket

Hi Jeebs, If you're experiencing call drops after initiating a transfer, I recommend following these steps to troubleshoot the issue: 1. **Verify Vapi Forwarding**:Use the Vapi API to confirm that the call forwarding is being initiated correctly. You can check the

endedReason

in the response to see if it shows

"assistant-forwarded-call"

. Here’s a code snippet for making the API call to check this:

bash
   curl -X GET "https://api.vapi.ai/call/{call_id}" \
   -H "Authorization: Bearer YOUR_API_KEY" \
   -H "Content-Type: application/json"

2. **Check Assistant Configuration**:Ensure your assistant configuration doesn’t contain

"phone-call-control"

in the

serverMessages

setting if you're not implementing custom call control. Ensure

phoneCallProviderBypassEnabled

is set to

false

. 3. **Review Telephony Provider Logs**:If Vapi did forward the call correctly (as indicated by

"assistant-forwarded-call"

), the issue may reside with your telephony provider. Check the provider’s dashboards (Twilio, Vonage, Telnyx) for any transfer-related errors using the

phoneCallProviderId

from the response. 4. **SIP Trunk and Packet Analysis**:If you're using SIP, consider downloading the PCAP file to investigate SIP signaling issues with Wireshark. Look for

REFER

packets to determine if the transfer request was sent and accepted by your SIP provider. For further assistance, refer to the [call forwarding troubleshooting guide](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops).