FNB incompetency *****ing money

I emigrated to the UK in August 2020 and have been trying to close both my business and personal account with FNB for about a year now. I have filed official complaints and tried numerous times to close these accounts. Staff at FNB have told me my request will be actioned only to find that nothing has been done. I now have received a letter of demand for my business bank account which should have been closed already. I have done everything in my power to close all of my accounts and have been paying for the accounts for far longer than I wanted to due to this incompetency. FNB has now ****med out of money for months and still refuses to close my accounts!