Waiting weeks for paid up letter!!!!!

I’ve settled my overdraft at FNB weeks ago. After settlement I’ve requested a paid up letter. I didn’t receive it. Last week I called them, they told me it will take 24-48 hours in order for them to send me the paid up letter. It’s a week later and I haven’t receive anything and the account hasn’t been closed as per my written request. This is totally unacceptable because the bank cost is accumulating again!! Now what???? I will close my business account, personal account and savings accounts and move to another bank! I don’t need this!!