FNB ****ming me of and unknown 4 year old debt

I was debt review and contacted all institutions I owed money (this is including FNB), they sent all debts associated to my name, I paid them all off and was able to receive a clearance letter from the court as I had showed that I have paid all debts associated to my name.

After receiving the clearance certificate, FNB then came back and said I had a debt from 2020 and that they had communicated this to me and my debt review company back then. I have never acknowledged this debt nor have I been contacted by any of their legal team regarding this debt. The interest for this debt keeps increasing monthly but when I try contact them via call or branch, they keep sending me around and my interest keeps increasing.

I honestly feel ****med by them and this is why I want to close my personal account and move to another bank that will treat its clients better!