FNB!!! Bad service

FNB has left me no choice but to go onto a public platform to raise my frustrations and lack of assistance!!!! I have been harassed daily for the past 3 weeks by the Debt credit card department for my "so called outstanding credit card" amount that is overdue. Consultant after consultant they call me - and my response to them is this has been settled and cleared last year October!!!! I have communicated and share this official FNB letter stating that this has been cleared and this account is officially closed. I even shared this letter with Malungelo Mseleku , one of their collection agents, on the 22 April. Needless to say, the phone calls continue!!!! This is a huge problem as my name is being listed as a non payer, when in actual fact, all outstanding accounts with FNB has been settled and closed in 2019!!!!! I will be handing FNB over to the NRCS within the next week, and then they can assist and get this cleared. As its stands I know FNB is marking my name as 'non payer' on a daily basis (as per credit score) and this is causing my credit score to come out super poor. I would expect a call from a senior and competent staff member who is actually willing to assist and finally update their systems and clear all the 'non payer flags' from my name! Should i not get feedback from FNB within this week, I will seek legal advise on this matter and take this up!