Day light *******

I paid off the credit card but they still debited R1520 month end of September. I called and sent email asking them to rectify that mistake as per case number ***. What they did now is they deposit that amount into that credit card that i asked them to close and took interest of around R800. The question is its an interest from which amount because i paid the account off and asked them to close it. I am now forced donate to Nedbank because they will debit and take interest on amount that im not owing.