Money removed from my account

Someone has implemented a debit order against my account and Standard Bank say I must have agreed to it, and thus refuse to help me. I do not know the person or company who has implemented the debit order, the bank keeps saying it must have been agreed to by me, which it wasn't. So basically someone can take money from my account every month and I can't do anything about it. My only recourse is closing the account and moving to another bank.