Paying for ABSA's mistakes

I moved from ABSA to FNB 3 years go.(Best thing ever) I went into a branch and closed all my accounts. I had a credit card that I also wanted to close. I got the amount outstanding from the lady and made the payment asap. Last week I got a message stating that my credit card has money outstanding. I asked that they please explain this to me. Seeing that I have not used this account in three years. I do not even have a card any more nor do I have any information regarding this account. I was told that I ow them R100 or something of this sort and that I will get a bad record if I dont pay it. I do not understand how this is possible that three years after I closed the accounts this can come back and haunt me... Or way, I should have known that ABSA would not do what was asked and doesn't care how they make money, as long as they do. I now have to pay for a mistake that their *********** staff made! I do not see how that is fair!