UNAUTHORIZED DEBICHECK ON MY ACCOUNT, HOW?????

Had an UNAUTHORIZED Debicheck go off my account which I did NOT authorize, According to ABSA you cannot reverse a debicheck, but I want to know WHY? and HOW? So this means that anyone that has your banking details can put a debicheck on your account without you authorizing it. That is scary. When you go to the bank (Brackenfell branch) NOBODY can tell you who authorized the debicheck and they cant reverse it either? Isnt that the same as ***** or theft? I demand answers. I will also not be paying the bounced debit order fees as there isnt any money in that account in the first place. Now ABSA wants the debit order that came back's bank charges from me? They can do as they wish. Will take this matter to the Ombudsman if I have to.