Unauthorised Debit Order

From time to time my account is attacked by *****sters who come to deduct my account in the form of debit orders. What is weird is that the charges for reversing and stopping something I know nothing about is the same amount of the debit order deduction every time it's like that. Why must I pay to stop my account from being de*****ed, when this is not even my fault? Why is my FNB account not safe?