HOW can a bank not be able to tell you which account is in arrears??

Once again, still no progress, despite (once again) numerous e-mails, phone calls and promises. I was told to wait until the end of the month and then the issue will be resolved. It's the 5th of the next month already, still no luck. Seems like FNB is becoming as *********** as ABSA. Now suddenly the account not in good standing order is no longer a revolving loan, but a residual account. I've never had a car loan from FNB. HOW IS IT POSSIBLE THAT A BANK CAN NOT TELL YOU WHICH ACCOUNT IS IN ARREARS???