Unauthorised transaction

I have an account with Fnb business account I went to a branch to enquire about adding someone as a beneficiary, I was given information that it will not affect my account as I did not want the person to transact on my account, I was paid money in my account and then she went on and requested a card from a different branch and cleaned out my account within a space of 2 hours and then when I go to the Bank they telling me that I have her the signing powers which I didn't now FINN is trying to pass the buck and not take responsibility for their negligence.