Debit orders without my knowledge which can not be resolved

To who this may concern I went to Fourways Mall FNB on Friday. I could not dispute two debit orders online. One in April the 15 and again the 15 this Month May. I asked the consultant why without any of my knowledge that debit orders are going though. They could not verify why. It's from DiscBank( Discovery Bank) . They gave me a page with the person's Name on which is from Gary Alter. Telephone number ***. No email address. Address P.O Box 786722 Sandton 2146. On the top page it says EFT customer service information. Company name DEVELOPER writern like that. User code 9530 I feel that it not right to leave it like that.I would not like this to happen to the next person. I feel FNB is letting me down. How could they allow it to happen. That I have to phone this person and ask them why are they debiting R500 every month? I did phone the number but no answer. I no longer deposit money into my account. If I can not resolve this,maybe it's time to change my bank account. Please may you help me in this regard?