Really the extensions.conf is simple:
exten => _[013].,1,NoOpe(${EXTEN})
exten => _[013].,2,Dial(ZAP/g1/${EXTEN})
This works well for numers starting with 0. With 3 it dials, but seems not
able to get in touch with mobiles.
I think it's a Dialplan setting problem...
Ciao and thank you
Mauro