FNB WONT CLOSE MY ACCOUNT

I asked FNB to close my account because I am not using it ,they told me they can not do that until there are no outstanding fees, and to my knowledge i had settle everything. They said they will look into it and close the account, this was a few months ago, this morning when I went to the branch they told me they could not close the account and now I have to pay for the past two months. I asked why am I paying for a service that I am not using, because i told them to close it! they said the system does not allow them to do that! now i have to pay for a service that I am not using, and its their fault bcos i had settled my account at the time i asked them to close it! FNB stop holding us ransom, you can not make me pay for a service I am not using.