SIP Trunking Issue Outbound Calls
# supports
steffenxyz_
05/02/2025, 3:23 PMI have the following issue.
I imported a number via BYO SIP Trunking from Telnyx to VAPI.
It works seamlessly for inbound calls.
But outbound calls from the vapi dashboard fail. It always states: call queued successfully but never calls. When I investigate, it seems the issue is the following:
I try to call a german number: +49...
When I follow this:
curl --location 'https://api.vapi.ai/call/phone' \
--header 'Authorization: Bearer YOUR_VAPI_PRIVATE_KEY' \
--header 'Content-Type: application/json' \
--data '{
"assistantId": "YOUR_ASSISTANT_ID",
"customer": {
"number": "CUSTOMER_PHONE_NUMBER",
"numberE164CheckEnabled": false
},
"phoneNumberId": "YOUR_PHONE_ID"
}'
and test it in curl from my CLI and use:
CUSTOMER_PHONE_NUMBER = +49XXXXX -> it never calls.
but when I put: CUSTOMER_PHONE_NUMBER = 0049XXXXX it works.
So I think there is some issue in how the telynx sip trunking works? This also affects the transferCall function
phone number ID: c32946de-2b04-419f-80bc-67008f55c8b0
assistant ID: 66febb4b-536f-4a30-b849-5dfd6f4816e6
v
Vapi Support Bot
05/02/2025, 3:25 PMAccording to the Telnyx integration documentation, when making outbound calls, the "+" sign should be omitted from phone numbers. This explains why
0049XXXXX+49XXXXX Copy code
bash
curl --location 'https://api.vapi.ai/call/phone' \
--header 'Authorization: Bearer YOUR_VAPI_PRIVATE_KEY' \
--header 'Content-Type: application/json' \
--data '{
"assistantId": "66febb4b-536f-4a30-b849-5dfd6f4816e6",
"customer": {
"number": "0049XXXXX",
"numberE164CheckEnabled": false
},
"phoneNumberId": "c32946de-2b04-419f-80bc-67008f55c8b0"
}'s
steffenxyz_
05/02/2025, 3:28 PMYes it works like this from Curl but it doesnt work from the VAPI dashboard. If I am in vapi under phone numbers and in outbound settings I want to make a call -> here when I select Germany as country it automatically puts the +49 apparently and the call never is successful. Kindly look into this
steffenxyz_
05/02/2025, 5:07 PMWhen I try via the dashboard, vapi shows a success but in Telnyx I see we try calling a number that is: +49-49XXXXX so we duplicate the +49 and hence the call fails
c
Chiranjeet Mishra
05/02/2025, 9:46 PMHey! To help track down this issue, could you share:
- The call ID
This would really help us figure out what went wrong!
s
steffenxyz_
05/04/2025, 8:39 AMthis is one example: abf87ce8-acc1-46aa-8d01-125c217d14dd
c
Chiranjeet Mishra
05/05/2025, 1:01 PMWe received 404 from Telny, for this call. Telnyx tried to route the German mobile number, got back “unallocated-number” from the PSTN, and relayed that as SIP 404. Double-check the number formatting and validity; if the number should exist, ask Telnyx to trace the call.
Chiranjeet Mishra
05/05/2025, 1:01 PMIf you require I can share the further details.
s
steffenxyz_
05/06/2025, 4:41 PMThe number exists and works. As I have stated earlier, if I use a curl command from my CLI it works when I put the number as 0049XXXX .... but it seems this is not what happens when I do this from the VAPI dashboard
steffenxyz_
05/06/2025, 4:41 PMThe issue must be only about the formatting of the pre-dial and country code
steffenxyz_
05/06/2025, 4:42 PMSo to sum up, if I try it via the VAPI dashboard it tries to call: +49XXX -> hence we get the 404 error. I get the same when I try to do this from curl with +49XXX as number. But when I test in curl with number: 0049XXX it works - this is the error
c
Chiranjeet Mishra
05/06/2025, 10:05 PMCan you try one call without the + symbol and with E14 check set to false?
Chiranjeet Mishra
05/06/2025, 10:05 PMLet me know how it goes for you.
s
steffenxyz_
05/07/2025, 2:16 PMalso doesnt work - this is the call ID: a7375424-a1ed-48b2-9c16-076b13e21b26 - I get the same error
steffenxyz_
05/07/2025, 2:16 PMIt only works with 0049: see this example: 8b88b1df-492d-47d4-8b5c-c1cf2f9fdb97
steffenxyz_
05/07/2025, 2:17 PMBut when I do it from the vapi dashboard it never works
c
Chiranjeet Mishra
05/08/2025, 2:39 AMLet me do a review and get back to you.
Chiranjeet Mishra
05/10/2025, 3:32 AMThe TransformPhoneNumber transformer would normally handle this, but in the dashboard-to-Telnyx flow, the problem occurs because:
1. The dashboard correctly formats the number with "+" prefix (E.164 format)
2. The number is passed directly to Telnyx without transformation
3. Telnyx expects the number without the "+" prefix for outbound calls (as shown by the successful curl test with "0049XXXXX")
s
steffenxyz_
05/11/2025, 8:42 AMOkay thanks for these insights. Is this then getting fixed? Or how can I get this to work for my use case?
2 Views