Maybe I can help you, I'll try anyway. Are you sure you have the service books? Options>Advanced Options>Service Books.
Options>Mobile Network>Network Technology: GSM/UMTS, Network Mode: 2G. It will not work on 3G, different frequencies on AT&T.
Options>Advanced Options>TCP/IP - APN: change this to wap.cingular, click on “APN Authentication Enabled” to put a check mark in the square. Username for APN: enter firstname.lastname@example.org. Password for APN: enter CINGULAR1. Back key, Save.
Sprint or Verizon 9630? If Verizon, press Send key, type ##000000, Send. CDMA Service Edit Screen will appear. Enter your area code and phone # after Mobile Directory Number:. BB key, Save. The phone will reboot. Your # will now appear on the phone when you make a call. On Sprint 9630, you must know you MSL (?) number, and I don't know how to get that if you don't have3 an account with Sprint.
This should get it working.