Un authorized debit order

On the 1st of August I got notification from my bank FNB of an debit order from from absa .what suprised me is that how can an big bank like absa took my money without my authorization. Worse the reference from notification says smart J . I don't know what is that.when I went to FNB to check they told it's absa .so absa can't do as they please in people's account. That's *****. I need clarity about the debit order. An they can't do as they please in my account. Worse party is that when I call the number that was given to me by FNB it's not working .If absa is used ny ****s to gain profit from poor its not a good thing