Call File

Channel: SIP/1001
CallerID: 919701777704
Context: my_extension
Application: DIAL
Data: SIP/1002
Set: UNIQ=101010

Dialplan

[my_extension]
exten => _X.,1,Answer()
exten => _X.,n,Set(CDR(userfield)= ${UNIQ})
exten => _X.,n,Dial(SIP/${EXTEN},20)
exten => _X.,n,Hangup()