Extremely disappointed with FNB

I am disgusted with FNB, I have banked with them for years I have a personal loan with them. My salary date is the 28th of every month. This month my Fiancé sent me money early because my son is sick so they have decided to debit my account today and I am left with nothing can't take my son to the doctor because they have taken the money. contacted their support and they said my debit order date has always been the 25th. how is that possible because my salary date is the 28th!!!!