Unauthorized Debit order transaction

My account has a debit order transaction that ran and when I went to FNB branch in Sunninghill on friday 08/01/2015 the consultant said she does not know why there is such a transaction and she cannot reverse. She phoned their call centre and Justin Pillay assisted and he also did not know why there is such a transaction on my account and he said he will find out from management and get back to me in 15 minutes. He never did. My account still reflects the debit order, I have to pay for something I don't know!!!!