What is the hand-off to the Rightfax/Opentext?
If it's PRI then there isn't anything you can adjust in the ATLAS - the called party number is part of the SETUP message sent on every call. If it is an RBS T1 then you may need to enable Direct Inward Dialing or change the SIGNALING METHOD if it is doing something like FEATURE GROUP D. (Feature Group D uses E&M Signaling with the DID digits being transmitted as *ANI*DNIS*)
Hope this makes sense,
Since there has been no follow up on this question, I'm going to mark it as "assumed answered." If you have additional information or questions please post them.