Bullying by attorneys jus because they can

Out of nowhere they called me about a debt that I didn't know about that I owe fnb for my business account debt from 2023 funny thing my account is active and my bank has never asked me for any payment or whatsoever, well I decided to pay regardless called them if they received the money they said yes account has been settled then I asked for settlement letter NO Response! Then today I'm receiving messages that I did not honor my arrangement! How when they rep**** me that account has been settled?