Debits more than agreed to/ No customer service from accounts

I just received a phone call from these guys accounts department regarding my outstanding balance of R129.00. Yes i am aware as i reversed my installment of R149 due to the fact that the arrangement was for my outstanding balance of R92 and my monthly installment to be debited, but then they go and debit me a total of R280 when my total balance should have been R244 total debit. When i tried to explain it to the lady from accounts she does not understand at all, and when asked if it is fair for them to debit me R280 when my outstanding balance is only R244 she wants to look for excuses to try and BS me with when she can simply give me straight logical yes its fair or no its not fair answer. If this is how they want to operate and the agents they want contacting clients i would rather then want to speak to the higher management as they might have a bit of logical common sense to understand that if i owe them an amount that they are legally only allowed to debit that amount as per my arrangement and not a cent more and should they debit more than what was arranged and agreed to i do stand within my legal rights to reverse a payment as the amount was not agreed to.