When doing attended transfer (A -> B -> attended transfer -> C) C only updates its caller id display when it answers the call. Is there anyway to update caller id on C, when B transfer the call while its still ringing?

The problem is we have some Cisco and Samsung SIP phones that does not have a real "Blind Transfer" support. If you want to transfer without talking to "C", you just press the transfer button quickly, while C starts to ring. So I want to send the updated caller id to "C" after "B" transferred but before "C" answers.

I have Yeastar PBX (asterisk based) works just like that but I can't  figure out how to do it with freeswitch.

Regards,

Rahman Duran