Unable to Find an Old Charge

I was an Att&t Uverse customer about 8 years ago and closed my account about 5 years ago. I have recently had a credit ping claiming I owe a collections agency $91 on behalf of Att&t Uverse. My account is considered inactive and I am unable to log in to check any past bills for whatever balance they are claiming. I very distinctly remember closing the account in good standing and returning all the equipment. I also do not recall ever receiving a bill from Att&t saying otherwise.

How do I access my old account to verify this before contacting Att&t or the credit bureau to dispute this?