Unhappy Fnb client

Good day. I have not a good experience from Fnb Rustenburg. I paid up my credit card in 2012 and have correspondence that the account has been paid up. Me and my wife are buzy to buy a house and all of a sudden Fnb let us know that my credit card is up for collection. I instructed Fnb in 2012 to close my account and never used it again. Now they put me on the credit bureau. I went to solve the problem and the put me on a phone in the corner of Fnb tp phone the credit card devision. After they put me through to the six'th person nobody could help me and I went to the consultant to help me. He hold the line for 3 hours only to give me a letter from a attorney which stated that the account is paid in full. We need feedbavk from Fnb to tell me what is the outstanding amount and why is the account not closed. I suppose it was costs on the account which was running on fro 2012. I send a letter via my wife's banking app but nobody reply back to me. I need them to clean my name from Itc. Thanks so much!