Closing business account

I have been with FNB for over 20 years. As long as you don’t need FNB to do anything for you they are a fantastic bank. Due to Covid my business folded and I needed to close down my business account. On the 10th of July I phoned closed it and paid in the money they requested me to yesterday I phoned asking why it has not been closed yet they would apparently get back to me today I log in and see my account is in a deficit. Every time I phone these people it cost me money now apparently I will also have to pay the fees incurred because of a debit order that went off.