9620L to be configured to dial only extensions

[tobor2bnot]

I got bit confused as to how do I block Remote IP 9620L handset from using any phone line be it PSTN/SIP through VPN tunnel. I just want the IP handset to dial out only the internal extension. I have got both PSTN and SIP lines configured. I don't want IP handset to pick any of these line for outgoing.....Is any across this. Would be very helpful and appreciate if anyone could guide here...

 

[cruzades]

Barred it to dial 9.

 

[amriddle01]

Or just tick outgoing call bar