We have a PRI for our trunk to the PSTN. It seems that whenever anyone calls out from any IP Phone to the PSTN the number that shows up on the recipients call display is the primary number of our T1 trunk. I want to override this so that the DID number associated with individual IP phones is the number that is displayed at the recipients phone on the PSTN when they have call display.
I have filled in the "External Phone Number Mask" field in the "Line Settings for this Device" section of the IP Phone configuration but it does not seem to work.
My Route Patterns are all configured such that the "Use Calling Party's External Phone Number Mask" is checked off.
Is there some other place I should be looking or am I missing something?