register for live tech help online...trying to call cingular and finding the right person to help you will take many tries. After logining in the chat room. Pretty state that you have a data plan and your device will not connect to anything that is WAP access. the tech will take care of it. so far has worked for me the 2 times i needed it done.
Your account is probably missing a simple line that enables WAP access in it that sometimes will get over looked when being setup.
takes a few min and best part you are not put on hold.