GETTING DEBITED FOR A LOAN I CLOSED OFF LAST YEAR!!

I took an ATM loan in December 2018, within less that 10 days I had paid the load off. Today 23/01/19 I open my online banking app and I find that I have an outstanding R63.80c towards a loan I had paid off. I called the loan department to find out what is going on, apparently I payed my loan off too soon and so my balance of R0 is mysteriously GAINING INTEREST! WHAT THE HELL??

As if that was not bad enough, I am told that this coming Friday I will be debited R1500 as this would have been the day I make my loan repayments. The consultant then goes on to tell me that I must call FNB back to reverse my money and that it could take a month before I have it back. This BS is unacceptable, I finished paying off this loan i December and it should not be building interest and I should not have to be debited. The idiot who is behind these systems better get it fixed before Friday. FNB is a lame excuse for a bank!