Hi
This is something you will need to check with the major credit bureaus. You are entitles a free credit report from them once a year. There are also other free and paid services that will give you that information. AT&T wont know this kind of information. When setting up service, AT&T will pull a credit report, but AT&T doesn't have a free access to it at later time.
Please let us know if you have any other questions.
Thanks,
Dmitriy