Bad Service/No Service

I took out a personal loan with Nedbank. I called and asked for the settlement amount. The amount was then paid in full. However, I was charged Interest and admin fees a week AFTER the amount was settled in full. Despite phone calls and emails, nobody at Nedbank has bothered to give me feedback as to why I was charged these amounts AFTER everything was settled. I cannot complain about their service as there has not been any. I have been a client for over 30 years and to I am very disappointed in how far this institution has sunk. It use to be one of the top banks in South Africa, now it is certainly one of the worst.