Account still not cleared

I have a credit card with FNB , FNB then sent my account to Groenewald Lawyers and they sent me a threatening message that I was owing 37k which I then pay 3 days later and then I was told everything was forwarded to FNB to my surprise they have not because when I phone FNB telling them I want to close my credit card they tell me they can’t close my account because it’s still has not been cleared meaning I am still owing my credit card which is not true . The Groenewald agent who was dealing with my account is Nanette. Please fix this it’s stressing me and I have stress because of your company . I am not happy at all . Why must it take this long for my account to be cleared ? I paid on the 20 of January