ITC listed and no one will help to resolve it

I have been listed on ITC for some years now for the original debt amount of around R10k due to direct debits being processed on my account after I had requested the account to be closed. I have tried to contact Nedbank on numerous occasions in the last ten years after receiving phone calls from different debt collectors but no one seems able to help me. Ten years later and the most recent message from another debt collector, the amount they are chasing me for is now over R70k and I am still no closer to resolving the issue and am still listed. I am trying to get finance and this will affect my credit rating so need this sorted out ASAP please.