Unauthorised opening of account in my name to which monthly charges are added.

I have(or had) a business Zero account with FNB and somewhere during last month it was automatically changed to a Gold account without my approval or permission. When I asked about this they said the upgrade is free since I met certain criteria. I asked about the charges and they said it remains the same(zero monthly charges). Today I log in to find a negative amount on my account for monthly charges. I got in contact with them via secure chat to be advised that I cannot downgrade and that I have to open up a new account. When explaining to them what happened they said they will double check then the chat timed out. Next they will take my Ebucks to cover that amount. Absolutely pathetic and unprofessional. This from people you entrust your money with.