SIP Call Transfer Issue – REFER Not Sent in Single Prompt Mode
Hello VAPI Support Team,
We are currently facing a SIP call transfer issue when using the single prompt transfer call function with our Netgsm (Turkish phone provider) SIP trunk.
When we perform a call transfer via Workflows, everything works correctly. A REFER message is sent to Netgsm, and the call is successfully transferred.
However, when we try the same transfer from a single prompt, Netgsm only receives a BYE message instead of REFER, which causes the call to be dropped instead of being transferred.
We already confirmed this with Netgsm support:
Workflows → REFER sent → transfer works
Single prompt → BYE sent → call terminated
It seems like the single prompt transfer function does not generate the SIP REFER request, unlike the workflow transfer.
I am using the same transfer_call tool in both workflow and single prompt but i cannot forward the call in single prompt assitant
Could you please check this on your side and confirm whether this is a limitation or a configuration issue?
If possible, we need the single prompt transfer to behave the same way as workflow transfers (sending REFER instead of BYE).
Thanks for your support.
Best regards,
We are currently facing a SIP call transfer issue when using the single prompt transfer call function with our Netgsm (Turkish phone provider) SIP trunk.
When we perform a call transfer via Workflows, everything works correctly. A REFER message is sent to Netgsm, and the call is successfully transferred.
However, when we try the same transfer from a single prompt, Netgsm only receives a BYE message instead of REFER, which causes the call to be dropped instead of being transferred.
We already confirmed this with Netgsm support:
Workflows → REFER sent → transfer works
Single prompt → BYE sent → call terminated
It seems like the single prompt transfer function does not generate the SIP REFER request, unlike the workflow transfer.
I am using the same transfer_call tool in both workflow and single prompt but i cannot forward the call in single prompt assitant
Could you please check this on your side and confirm whether this is a limitation or a configuration issue?
If possible, we need the single prompt transfer to behave the same way as workflow transfers (sending REFER instead of BYE).
Thanks for your support.
Best regards,
