(this is from extensions_additional.conf):

[ext-did]
include => ext-did-custom
exten => 18007680189,1,Set(FROM_DID=18007680189)
exten => 18007680189,n,Set(FAX_RX=disabled)
exten => 18007680189,n,Goto(ext-local,200,1)
exten => s,1,Noop(No DID or CID Match)
exten => s,n,Answer
exten => s,n,Wait(2)
exten => s,n,Playback(ss-noservice)
exten => s,n,SayAlpha(${FROM_DID})
exten => _[*#X].,1,Set(FROM_DID=${EXTEN})
exten => _[*#X].,n,Noop(Received an unknown call with DID set to ${EXTEN})
exten => _[*#X].,n,Goto(ext-did,s,1)

; end of [ext-did]


[ext-local]
include => ext-local-custom
exten => 200,1,Macro(exten-vm,novm,200)
exten => 200,n,Hangup
exten => 200,hint,SIP/200

; end of [ext-local]