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# support
d
v
Thank you for sharing the details. To help troubleshoot the "Call.in progress.error" transfer failure, could you confirm if your "transfer_call_tool" configuration includes the required "destination" parameter (the phone number to transfer to, in E.164 format)? Missing this parameter is a common cause of transfer issues according to the documentation. If possible, please check your tool's parameters and let me know if the "destination" is set up correctly. Sources: - [Vapi documentation: call forwarding](https://docs.vapi.ai/call-forwarding) - [Debug call forwarding drops](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops)
d
It looks correct to me @Vapi Support Bot
v
Thank you for confirming your configuration. Could you check if your assistant's configuration includes 
"serverMessages": ["phone-call-control"]
or if 
phoneCallProviderBypassEnabled
is set to 
true
? These settings can override Vapi's call control and cause transfer failures, according to the documentation. Let me know what you find so we can proceed. Source: - [Debug call forwarding drops](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops)
d
There is no such thing as "serverMessages" or "Phone-call-control" or "phoneCallproviderbypassenabled" in my assistants configuration JSON, But I am also NOT able to edit it as I am in the web interface dashboard @Vapi Support Bot
v
Thank you for the update. To help narrow down the cause, could you please check the "endedReason" for your failed call (ID: 019ab5d9-7ce2-755b-a0ef-8dea4bb7a1fb) in the Vapi dashboard or via the API? This value will indicate whether the transfer was initiated or blocked by configuration, which is a key step in troubleshooting according to the documentation. If you can share the "endedReason" value, I can guide you on the next steps! Source: - [Debug call forwarding drops](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops)
d
Ended: Call.in progress.error transfer failed @Vapi Support Bot
v
Suggestion: Please double-check that your transfer destination number is in the correct E.164 format (e.g., 
+35312345678
for Ireland). Try calling this number directly from your phone to ensure it is reachable.
Copy code
json
"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["+35312345678"], // Replace with your actual number
      "description": "The destination to transfer the call to."
    }
  },
  "required": ["destination"]
}
If the number is correct and reachable, review your Twilio call logs for any transfer errors. Source: [Debug call forwarding drops](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops)
d
Copy code
{
  "id": "58bc5653-f8c6-4450-b6d9-61b1cbb4350b",
  "createdAt": "2025-10-19T17:59:36.705Z",
  "updatedAt": "2025-11-24T13:09:08.656Z",
  "type": "transferCall",
  "function": {
    "name": "transfer_call_tool"
  },
  "messages": [
    {
      "type": "request-start",
      "content": "",
      "blocking": false
    }
  ],
  "orgId": "117c82dd-62c3-421e-9e72-2a31d32a1a12",
  "destinations": [
    {
      "type": "number",
      "number": "+49173REDACTED",
      "message": "Einen Moment, ich werde Sie weiterleiten.",
      "callerId": "REDACTED",
      "description": "When they want to speak with \"REDACTED\" you will forward",
      "transferPlan": {
        "mode": "blind-transfer",
        "sipVerb": "refer"
      },
      "numberE164CheckEnabled": true
    }
  ]
}
@Vapi Support Bot
v
Next step: Check your Twilio Console call logs for the failed transfer. Go to [Twilio Console > Call Logs](https://console.twilio.com/us1/monitor/logs/calls), search for the call using the 
phoneCallProviderId
(e.g., 
CAabc123
), and look for transfer-related errors in the call timeline. This will help pinpoint if Twilio rejected the SIP REFER or if there’s a provider-side issue. Source: [Debug call forwarding drops](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops)
d
@User
@Vapi Support Bot did you see the logs?
Fixed it as I changed twilio routing to US
a
hey @DNP i am having a similar issue where we are paying for the transfer minutes after the transfer, are you seeing similar with twilio?
right now we are using a telephony connected number to transfer
c
Hi DNP, If you encounter issues while using the transfer tool, it might help to ensure that the correct transfer destination type is being used (
TransferDestinationNumber
or 
TransferDestinationSip
). Additionally, check if the 
transferPlan
has the appropriate 
mode
and if the 
message
or 
sipUri
fields are correctly configured. If you're experiencing server errors or call failures during the transfer, refer to [this document](https://docs.vapi.ai/api-reference/webhooks/server-message) for detailed error codes and messages. This can help troubleshoot whether the issue is related to quota limits, authentication, or anything else specified in the error descriptions. For creating a transfer tool or checking configurations, the definitions and required fields for creating a tool can be found in the [tool creation API documentation](https://docs.vapi.ai/api-reference/tools/create). If the problem persists, please check your setup against the documentation to ensure all parameters are correctly used.
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