UNHAPPY with the service I am getting from DebtBusters SA after settling my debts

I have been under debt rehabilitation under debtbuster for over 2 years nor, I lost my job to retrenchment and I settled all my debt, I sent an email with all the proof of payment and instructed them to cancel the debit order and send me a clearance certificate. I got an email response from Neo Mongale saying that are unable to reduce the overall instalment as my debt review term was calculated based on your total instalment at inception. I fail to understand why would they still debit my account when all my debts are settled, what will they be doing with the money they will be debiting from my account? They actually want to keep taking money from people that are struggling. I believe my contract with them is null and void as I am not owing anyone anymore.

The sad part is they even blocked my bank to stop the debit order from their side, and they are the only ones that can stop it, the best way is to cancel the account number they debiting from and to open a new account number which is stress but I am doing that cause R3000 is a lot of money to give for no reason,

I would appreciate to hear from them otherwise I will report them to the NCR ombudsman