fnb can't just keep debiting my account

I had an arrgement made with fnb to debit my account on the 25th every month. I even had payments taken out all the time from fnb. My kids have not been to school yet cause I didn't buy them uniforms. Yesterday I asked a friend to loan me money to buy them school clothes this morning I get up and fnb took all of my money. How can they keep taking money from me without my permission. I'm sitting at a branch now and called a lady from the loans department telling her all this she says sorry it cannot be reversed. I can't believe FNB is worse then SARS this is ruthless and u acceptable. I inositol on getting my money back today so I can have my kids sent to school. And I am closing this account totally I think I was better of with standard bank