Worried About Credit Score/Possible Cyber Security Issue Uverse/Internet Service Payment

Hi-

My long-time ATT Uverse/internet service was shut off by ATT.

I was able to reach a real person with ATT to ask what was going on.  The ATT representative said service was turned off for nonpayment..that I hadn't paid the bill for SEVERAL MONTHS prior to a May 2nd payment.

ATT says I haven't paid the bill from December 2023 to May of 2024

I had paid the bill at least three times in that time period.

The ATT representative said they had a record of the payments during that time-and gave the last four digits of the credit card used, and a check I had written.

NONE of the credit card last four digits  the represenative listed were from my credit card (including any prior credit cards.)

Same thing with a prior check-the last four digits of the account were NOT mine.

So what the heck is going on?

I looked at my bank statements--and there is NO record of any credit card payment or any checks between May and December made to ATT.

Is there some kind of bizarre hack going on..and now I'm worried the NEXT payment will also not be credited.

Thanks