Fnb *****ing money

I woke up yesterday just to check my account because I knew had R49 left . To my utter shock I discovered that my account is on a negative balance of -R2593 , I have no debt orders on my account except R59 for iCloud . I’m expecting my salary literally 6 days from now . And my account is still on - . I’m really thinking of just switching banks because I’m tired of these ******* just taking my money for nothing . How am I expected to part with almost R2600 for something I don’t even know? I hate FNB