Unable to assist with unauthorized Debit Order

I have called FNB since this morning regarding ********** activity that happened in my account I spoke to two ladies from customer service and two ladies from the debit order department and Lawrence from the ***** department who was rude enough to tell me that I am wasting my time speaking to him I should call the debit order department which told me they can't do anything about this debit order. How does someone debit my account with a mandate in please isn't what this debicheck system suppose to protect us from such activities???? I am very disappointed with FNB considering I have been banking with them for years and what this matter sorted out