Discovery bank debit order not approved though FNB

They have a debit order in my FNB *** is been taken every month on the 15. Today I went back to FNB. They called Discovery bank on my behalf. FNB can't help as usual like the last time last Friday. They say at Discovery bank I have a credit card. What a shocking Discovery. I have never signed for one every in my life. The only bank account I have is FNB. I asked them who gave them the right to approve with my DETAILS. And who signed for that debit order which first started on the 15 May of 500. I have never equired for a Discovery bank ever. They said they going to investigate. They can not answer me. And also how much is this credit card ? Owing or what ever has been done with it. I asked the guys DETAILS to follow up. He said he can not give me his name and telephone number. He only gave me a *** number. He said it will take 7 working days to get back to me. Sad reality. I wish this thing could me sorted out. Heart broken