harsh-harlequin•3d ago

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,