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Vonage forwarding is not working
# support
l
Hey @Vapi team. We're having some issues when trying to Transfer the call to a Vonage Phone number. I couldn't find any error in the logs. The logs are shown that calls are being transferred, but after that, we're getting single ring calls with no caller connected. How can I find the log errors for these issues?
j
It looks like the transfer is triggering, but the SIP leg to Vonage isn’t fully bridging that’s why you’re getting a single ring with no caller. This is usually a SIP header issue (From/PAI), early BYE from the carrier, or transfer type mismatch. I’d check the detailed SIP logs (INVITE, 180/200 OK, BYE) on the carrier side to see where it drops. Are you using direct SIP trunking with Vonage, and does this happen on all numbers or just specific ones? @Leo
c
could you please provide the call id from the call logs where this issue occurred?
l
019c7227-bc89-700d-a4e1-ed640912acf6
Sorry for the delay @James Christopher . Just this number is reporting this issue. We don't have much usecases for Vonage now.
Also, the Vonage phone number was imported from Vonage in Vapi using the import feature
j
Thanks for clarifying. Since it’s just this imported Vonage number, the issue is likely a SIP mismatch or carrier-specific drop. We can check the SIP trace to pinpoint the problem. Do you want me to guide you on pulling the detailed logs for this number? @Leo
j
l
I appreciate @James Christopher
@Jeebs from eva.be did you resolve this issue?
In case of SIP mistmatch, what are possible fixes @James Christopher ?
j
Appreciate you checking in. If it’s a SIP mismatch with Vonage, the common fixes are aligning the From / P-Asserted-Identity headers, confirming the caller ID matches a verified Vonage number, and making sure the transfer type (blind vs warm) is supported on their trunk. I’d also review the SIP trace for early BYE or rejected 200 OK to see exactly where it drops. Happy to jump in directly, review the logs with you, and adjust the config live so we can resolve it properly. @Leo
l
I appreciate. Are you available now?
BTW, the voice inspector shows just this error:
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CHANNEL:
Voice Failed

STATUS:
FAILED

DESCRIPTION:
Callee currently unavailable
I found something, for most transfers, we have a ebhook event for Phone Call Control - Transfer. But there are some calls here e don't have the message in the Vapi Webhook logs.
So, what I tried so far 1. Invoke the Phone Call Control via Curl while call is active using a Forwarding Phone number A ❌ 2. Invoke the Phone call Control via Curl while call is active using a Forwarding Phone number B ✅ 3. Do not start the call using Vapi Assistant Webhook request, instead return the
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return {
        status: 200,
        body: {
          destination: {
            number: fowardingPhoneNumberA,
            message: 'xxxx',
          },
        },
      };
✅ 4. Call normally and let the assiistant forwar dthe call using the ForwardingPhoneNumber A ❌
j
Thanks for laying this out so clearly , that actually helps a lot. The fact that Number B works and Number A fails, combined with the “Callee currently unavailable” message from Vonage, really suggests this is a carrier-side rejection on that specific number (most likely caller ID validation, SIP header mismatch, or a restriction on the number itself). The missing Transfer webhook logs also tell me the bridge may not be fully completing in those failed attempts, meaning the call could be getting rejected before Vapi finalizes the transfer. At this point, I’d compare SIP traces between A and B, double-check the caller ID / P-Asserted-Identity headers, and confirm there aren’t forwarding or trunk restrictions on Number A. I’m available now, send me a private message and we’ll go through it together and get this sorted properly. @Leo
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