with some headers like below:

recv 906 bytes from udp/[dst.dst.dst.dst]:8090 at 05:02:33.558626:
   ------------------------------------------------------------------------
   SIP/2.0 480 Temporarily Unavailable
   From: ""<sip:TCAPI_User@dst.dst.dst.dst:8090>;tag=8SN0g1DmHy0NF
   To: <sip:91001@dst.dst.dst.dst:8090>;tag=59f1478-33001dac-1f9a-50022-1f428f-b29b56e-1f428f
   Call-ID: 96685221-f5e9-1231-b1a5-000c29ae8315
   CSeq: 54415412 INVITE
   Via: SIP/2.0/UDP src.src.src.src:5080;rport=5080;branch=z9hG4bKtScUQtUy9rgmp
   Supported: replaces
   Info: {"MerCode":"102"}
   Sign: Ley1/8cOufqkgd7JuGR7f+jiVxSRM=
   BillPaymentList: {"paymentID":"16596500682","result":"0"}
   Content-Length: 0

I run /event plain all in my fs console and no variable exists like info, sign and billpayment in channel variables.

Any solution to catch response header?! I cannot define or change key of the headers. I should adapt to these keys!!!