Thank you for using the ADTRAN Support Forums, and I apologize for the delay in responding to your post, but I have been out of the office.
If I understand your situation, you are changing your connection to the PSTN from an RBS T1 to a PRI, correct?
If so, first make sure the SWITCH TYPE on the PRI is correct. In the ATLAS, "National ISDN" is "NI-2". It should match the Switch Type information given to you by the Telco.
If this is correct, then you should probably change the "Outgoing Number Conv" to "As Dialed" - then go to GLOBAL PARAM (under DIAL PLAN) and go into the NUMBER TYPE TEMPLATE. (This template is only used when the OUTGOING NUMBER CONV is set to "As Dialed".) Under the NUMBER TYPE TEMPLATES, anything in the PREFIX column is stripped off, and not transmitted, So you will need to move the "1" for long distance calls to be part of the PATTERN. So the PREFIX will be blank (highlight the "1" and hit ENTER and then BACKSPACE to erase it) and the PATTERN will be "1 (NXX) NXX-XXXX". I would go ahead and change the NUMBER TYPE to be UNKNOWN instead of NATIONAL as well.
Similarly, the international number should be changed as well, so there is no PREFIX and the PATTERN is "011 X$" with the NUMBER TYPE set to UNKNOWN.
It would probably be a good idea to change all of the NUMBER TYPEs to UNKNOWN just to be consistent.
Let me know if this fixes your problem or not, or if you need some clarification.
Since there has been no follow-up on this for quite a while, I'm going to mark the question as "assumed answered". If you still have questions feel free to change the status back to "Not Answered" and post any additional information you have.