Paid up and closed amex card now has a balance

I paid up my amex hold card in August 2021 and closed it. All of a sudden my clearscore reflects that there is R140 outstanding and it states that I have not paid for 20 months. I contacted them as I do not owe this and I want it removed off my clearscore. No one can help me in fact I was asked if I am under debt review...seriously no I am not and what has debt review got to do with a balance that suddenly appeared on a closed paid up account. I am not happy.