Unauthorised debit order

I am i arrears for my car for the month of July, i called Mfc to notify them and make necessary payment arrangements, i had an arrangement for 4 month to pay via eft, as i arranged i paid 1400 on the 27th of August via eft. And then on the 31 of August mfc made an unauthorised debit order on my account. When i called to ask for a call recording where i am agreeing to a debit order for that arrangement Gcabasi told me that she doesn't know when her manager will assist. Even after telling her that my account is over drawn and they debited an extra amount i didnt have in my account she said he manager Samantha will call me when shes available cause shes working from home. I need mfc to refund that extra amount back cause my account is now 1500 in arrears. I want mfc to cancel that debit order payment arrangement