extensions_override_freepbx.conf
[sub-diversion-header]
exten => s,1,Set(DIVERSION_REASON=${IF($[${LEN(${DIVERSION_REASON})}=0]?no-answer:${DIVERSION_REASON})})
exten => s,n,SIPAddHeader(Diversion: <sip:${FROM_DID:1}@ip_pbx>;reason=${DIVERSION_REASON};reason=unconditional))
exten => s,n,Return()
[sub-diversion-header]
exten => s,1,Set(DIVERSION_REASON=${IF($[${LEN(${DIVERSION_REASON})}=0]?no-answer:${DIVERSION_REASON})})
exten => s,n,SIPAddHeader(Diversion: <sip:PHONE_NUM@PBX_IP>;reason=${DIVERSION_REASON};reason=unconditional))
exten => s,n,Return()