Unauthorized Debit Order Date

Nedbank (MFC) have decided to debit my account on the 24 Feb without my authorization, the signed authorized debit order date is on the 27 of each month but greedy reason they debit 3 days before the date. There was no "DebiCheck " sent to me for my authorization. This is unacceptable behavior from Nedbank(MFC), because I have incurred debit rejection costs from my bank because there was no sufficient funds. Basically I have lost money due to this act by Nedbank.