debit order dispute

So fed up with FNB. I am unable to dispute a unauthorized debit order on my account with no assistance!! They say i must get my money back from the institution that has debited my account. HELLO!! ITS UNAUTHORIZED THEY WILL NOT PAY ME BACK!! The only way i will be able to resolve this is to close my account, and even when i said that i will have to close my account then, they said ok send us a mail and we will close the account!! useless bank!!!!!