Unauthorised debit activated on my acc by Nedbank Home Loan

I have been in contact with Nedbank home loan regarding the debit they activated without my concern or involvement. I paid off my bond on the 11th January 2004 and waited for the bank to allocate attorneys to cancel my bond. I waited for well over a month and I initiated the process of bond canceling. Only then was I allocated the attorneys. Now on the 2nd May 2024 my account was debited without my concern or authorisation. I then lodged a complain regarding this matter with emails going forwards and backwards. The apologised for the delay citing high volume of work. They asked me to send them a signed letter requesting for the refund and the banking details to which the refund would be allocated to which I did. Now this morning of the 16th I received an email that I would not be refunded because I have the outstanding amount that I owe. Here are a few factors: 1. Who gives banks the right to debit clients accounts without their concern or involvement. 2. Why does the bank have the right to debit a clients account as and when they feel they can don so. 3.Debit check must be authorised by the client before they can action it that much I know.