Copied from my previous post:
If your credit application was denied, the Equal Credit Opportunity Act requires creditors to specify why -- if you ask, it's the law. For example, the creditor must tell you whether you were denied because you have "no credit file" with a CRA or because the CRA says you have "delinquent obligations."
AT&T is required by law to tell you why you were denied credit(Apple is not providing you with credit, AT&T is). It is not optional on AT&T's part, it's required by law. Most companies, as a matter of routine, will automatically send you a letter, in the mail, detailing why you were denied credit. You should receive this letter within 10 business days from the date of denial. I'm not surprised that a CSR in an AT&T store or on the phone will/did give you a run-around. They most likely have no access to these credit decisions. Talk to an AT&T store manager.