NEDBANK credit card with arranged payments but no decrease

I have a credit card with Nebank and they handed it over to IDA but I am not happy on how they handled my case .The outstanding amount now is more than what Nedbank handed over to them> I made an arrangement to pay amount of R5000 consistently but still I was charged more interests and legal fees as if the account is active and I don’t have an arrangement. I have already asked to pay higher using an arrangement with no interests added but I am not getting an answer. I have already paid an amount of R70000 over the years but there is no decrease on my debt. This makes me have concerns as I am black listed and I am now more indebted than before the account was handed over to IDA.