How to use regex in extensions.conf

[TheMark]

you need to use ${EXTEN} after the match

@emir0723

[internal]
exten => _700X,1,Answer()
same => n,Dial(SIP/${EXTEN},60)
same => n,Playback(vm-nobodyavail)
same => n,VoiceMail(${EXTEN}@main)
same => n,Hangup()

exten => _800X,1,VoicemailMain(${EXTEN}@main)
same => n,Hangup()