https://vapi.ai/ logo
Join Discord
Powered by
Call transfer via Zadarma SIP
# support
n
Hello Team, I've created a transferCall Tool with a standard configuration. When the tool is triggered, the call gets disconnected. Call ID: e722b66e-75d5-4cd8-b47c-cecf97608031 Timestamp: 24/06/2025 14:17:59 UTC Tool ID: 2e280b0b-f96f-4f38-ad74-1708bffb7f0f I use a SIP and a virtual number from Zadarma. They work well for standard inbound and outbound calls made by VAPI assistants. Please advise if I need to apply any specific setup for Zadarma to make call forwarding work.
n
VAPI uses 
SIP Refer
to perform transfers - Zadarma doesn't support 
SIP Refer
as far as I can recall. Feel free to DM me for more details.
a
Same stuff. @User it's an essential feature, could you please look up into this?
n
I also tried Telnyx. Unfortunately, it didn't work too. Call ID: 11c1767e-55b4-4d3f-bdaf-70883fba98fd
@A Igor It seems that it's a known issue that has no resolution for now. https://discord.com/channels/1211482211119796234/1370592524053516298
k
p
Hello. Is there any update in regard to the issue? From zadarma perspective, they support SIP refer (I've got such info from thier support, the transfer method should be handled this way). However, it still doesn't work, the calls being rejected. By analyzing .pcap from VAPI calls logs "Session Initiation Protocol (501)" (not supported)
It was also mentioned, in IA assistant code it can be added something like this (please, see the code below). I do not get, what's the difference if the transfer_tool handles the method by SIP refer anyway or am I mixing it up with something else? Some advice on that? "{   "type": "tool_use",   "name": "call_transfer",   "parameters": {     "phone_number": "+1234567890"   } }
n
A 501 error from Zadarma indicates that the 
Refer
message is probably not formatted correctly.
k
Hey @protosartos, could you please inquire with the Zadarma team about the missing information in the REFER message body that's causing the 501 error?
n
Zadarma probably can't process the 
tel:
URI that you are using, which are the default for Twilio and Telnyx - as Zadarma isn't a CPaaS.
s
@Nir S (CEO/Founder @Cloudonix) thanks for your help. I'll look into what we can do for him. Meanwhile, do you have any recommendations that could work for him?
n
Implement the transfers externally via Cloudonix or Jambonz. It will also reduce his connectivity costs and potential AI over usage, in cases the AI doesnt hangup properly, due to various reasons.
s
Thanks. cc: @protosartos
PreviousNext
Powered by