SIP First Responder

[send-sip-response-code]
; Context to send a specific SIP response code and terminate the channel
; Create Custom Destination in FreePBX with a dial string of the format
;          send-sip-response-code,404,1
; substitute the appropriate response code in place of the 404
; Reference: https://wiki.asterisk.org/wiki/display/AST/Hangup+Cause+Mappings
;
; latest version: https://gist.github.com/lgaetz/480582a1827cc98db1ee539c249f074b
;
; License GPL/2
;
; History    2019-10-08   First attempt supports 404, 480 and 486
;            2023-04-14   added 501
 
 
exten => 404,1,NoOp(Entering user defined context send-sip-response-code in extensions_custom.conf)
exten => 404,n,NoOp(Sending SIP 404 Not Found)
exten => 404,n,hangup(1)
 
exten => 480,1,NoOp(Entering user defined context send-sip-response-code in extensions_custom.conf)
exten => 480,n,NoOp(Sending SIP 480 Temporarily Unavailable)
exten => 480,n,hangup(19)
 
exten => 486,1,NoOp(Entering user defined context send-sip-response-code in extensions_custom.conf)
exten => 486,n,NoOp(Sending SIP 486 Busy)
exten => 486,n,hangup(17)

exten => 501,1,NoOp(Entering user defined context send-sip-response-code in extensions_custom.conf)
exten => 501,n,NoOp(Sending SIP 501 Busy)
exten => 501,n,hangup(29)
 
; end context send-sip-response-code

Improvements from isaacgross1 on this thread
https://community.freepbx.org/t/freepbx-reject-calls-without-actually-answering-the-trunk/99416/12?u=lgaetz