Unsettled account on a Settled account

I would just like to express my disappointment and displeasure with NBA organization. I have settled my account as per the agreement. I have settled the account in April 2021 and to date i am still being harassed for an account that has been settled. I have sent them numerous emails and chats but have not received any feedback from them. The only emails i am getting is emails on outstanding amounts that has been settled already, They are quick to phone you about outstanding payments but when you inform them that the account has been settled they end up being rude or just hang up without closing they query or noting down that the account has been settled . Please advise as to how I can arrange for this matter to be sorted out as this is really annoying having to explain the same thing over and over again to different people on different communication platforms. I really this matter to sorted out urgently.