Added charges on a closed account!!

I just made a payment of more than R9000 to a closed cheque account, the account was closed in july and the debt written off. As per the banks letter dater august 2018 the amount owed was R9400, i paid R9500 into the account. To my surprise i am then told in september that i still owe another R4000. Wow im shocked. Is this standard procedure of standard bank? To ******* old clients? By the way your consultants agree that charges can not be added onto a closed account,especially when the debt on it had been written off.