Fnb refuse to refund my money

I want to know if it is legal for the bank to debit your account without your permission FNB refuse to pay me back where can I lay a charge against them as they were rude I spoke to Muneer. Davis that gave me no solutions she don't even know what is happening David from the complaints department was Very helpful he even told me that they closed the complain saying they can't get hold of me but when he calls me he gets hold of me. I need to take this matter further as the loan department have people that don't know how to treat customers