FNB gives your money away to anyone

I have a premier cheque account with FNB. Money was sent from my account without my authorization and when I called my so called team of premier bankers, they told me they couldn't reverse the transaction. How can this even be possible. I thought a bank is supposed to keep their clients money safe, what am I supposed to do now? I now won't be able to pay any of my accounts or buy food because of this. And I also need to resort to public shaming to get a little attention. What's happening FNB? Can you keep my money safe or is this not your problem