Un Authorised debit orders from FNB

I have a Personal loan with FNB and due to sircum stances I fell behind with my payments. Fnb then made arrangements with me that I am very great full for, but it seems that there is no communication with in FNB and their consultants. This morning FNB ran 4 debit order for 4 different amounts that the last arrangement was not included. Due to me starting a new employment my salary was not sufficient to cover the debit orders. Upon my inquiry with regards to the debit orders know one can give me an answer. They debited my account and due to no funds there is transaction fees of more than 500 rand that was debited against my account. I mean the bank can see if there is funds or not but putting a debit orders through that was not agreed upon is wrong and putting my bank account in debit with R1050 is just wrong and know one seems to care. The banks think they are Un touchable and that is just not right. I need help please.