Account Closed MONTHS ago - now blacklisted for it

I've closed my club account in MAY2020 - received a confirmation from Edgars that the account is closed. And I paid up in full. Then in September I started getting phone calls and smses saying my account is overdue. After explaining telephonically MULTIPLE times- after sending the evidence MULTIPLE times - no further investigation on their part - they STILL went ahead and blacklisted me for subscription fees POST May 2020. This gives the whole Edcon group a bad name.