Excessive balance after paying off my account

Some time last year I paid off the revolving credit I had with Standard bank, I was give a balance of R5700.00 and some odds which I had to pay to close the account. I then paid up the balance and asked for my account to be closed but I was told I had to go to the branch. I hardly have anytime to make it to the branch never and will never ever get time as I forever busy at work on weekends and during the week. A couple of weeks back I got a statement that showed that I owed R700.00 plus to standard bank. I am disputing all those charges as I have never ever used up any money from that revolving credit. I had a revolving credit with FNB and asked them to close it over the phone and that was done, I don't understand why Standard bank can't do the same thing. I will not pay any recurring costs as I have settled what I was told and requested it to be closed. This is just pure ******* and will have to take it up with the NCR if this persists.