SIP Trunk REFER - Remove PBX from Call path

[Tim Mrazek]

Is there a way to setup SIP REFER messages with providors to remove two calls on the PSTN from the PBX? A(pstn) > B(pbx). A is transfered\redirected to C(pstn). My providor supports a REFER message to drop the call on our pbx and free up a license.

 

[eddv123]

I am not 100% getting your need or requirement here, however what I would say is take a look at this:
https://www.3cx.com/docs/sip-trunk-options/

At least on the 3CX side see "supports replaces" as the guide states: This is used by the REFER method (RFC3515) and 3CX may use this when an external call is transferred to another external number.

At the very least this guide will give you the options available on the 3CX side.