Poor banking ethics

frustrated, I took a loan at Nedbank and I struggled with monthly payment, I at last find way to settle my loan with them to my surprise they never close my account after I asked for settlement and paid it off, it was 2020 October when I call they make it my problem the loan was never closed and it is still owing, I fail to understand why is it my fault as I paid it off within the given time, My worry is it going to ruin my credit history, I have been calling sending emails its almost 3 months now with no response from them and they are still debiting my account and I get those debit reversed.