with Voipjet also allows you to set your own CID. This is what I have for setting my own CID. I used random voice files because I was too lazy to record my own
exten => 100,1,Goto(Spoof,s,1)
;Exten that goes the spoofing context
[Spoof]
exten => s,1,answer
exten => s,n,background(digits/hundred)
exten => i,1,playback(pbx-invalid)
exten => i,n,goto(Spoof,s,1)
exten => t,1,goto(Spoof,s,1)
exten => _XXXXXXXXXX,1,Setglobalvar(cidtoshow=${EXTEN})
exten => _XXXXXXXXXX,2,Goto(Spoof2,s,1)
[Spoof2]
exten => s,1,background(digits/million)
exten => _XXXXXXXXXX,1,SetCallerID(${cidtoshow})
exten => _XXXXXXXXXX,2,Dial(IAX2/XXXX@voipjet/1${EXTEN})
exten => i,1,playback(pbx-invalid)
exten => i,2,goto(Spoof2,s,1)
exten => t,1,goto(Spoof,s,1)