PJsip extension with fixed contact

I have opensips frent-end for FreePBX
all phones were been registred into Opensips
this same extensions also created into freePBX for Voice mail
I want to if a call is generated from freePBX to extension it’s pass via opensips

I think, if I fixed AOR contact to point opensips like
[1200]
type=AOR
contact=sip:[email protected]_of_Opensips
How can I add this in freepbx in gui or in custom configuration file