Here is what happened. Your folk had a paid email account through ATT when they had DSL. When your folk registered for the new Uverse Internet they chose to "create a new ID" instead of "use existing ID". So now their familiar email is in no way associated with their paid Internet account. It is defaulted to a free ATT email. See »www.att.com/esupport/art ··· bGYmXCR2
Set aside some time and gather as many notes as you can, then contact Tier 2 and have them re-register the Uverse account with their old email address.