[Freeswitch-users] How to get SIP response string (not header)

Hi All, I'm looking for the possibility to get SIP response string from B leg, do some transformations and pass it back to the A leg. Example response from B leg: SIP/2.0 500 Trunk Prefix Mismatch When FS receives that response from B, it ignores text message "Trunk Prefix Mismatch" and send to the A leg reply with it's own message SIP/2.0 500 Internal Server Error How to get that response or pass it unchanged to the A leg? Best Regards