Failure to close my loan account

I am so disappointed in the poor service I received from FNB. I have been trying to close off my revolving loan account and after having paid the settlement amount all the account is still active. When I called to follow up why the account is still active then there's a new outstanding balance that I need to pay off which the consultant could not explain why the amount accrued. I waited on the line for over 20minutes to speak to the manager and still no luck. Instead the consultant told me to wait a further 5-7 working days for the feedback. In the meantime this account is accruing interest despite asking for this to be closed. I'm really frustrated and disappointed.