Debit card dispute

I canceled a debit card transaction with rain and I lodged a complain with fnb that I want to cancel and reverse the transaction, no 1 came back to me till today I left it and yesterday I withdraw all my money in my bank account so that rain doesn't get money in case they try to debit again this month ,guess what it went thru and left me on a minus on my account I want to understand why did they allow rain to debit whereas the is no money In my account because according to me it shouldn't go thru since the is no funds In my account I want fnb to fix this because I'm not going to deposit any money in my account until it's resolved meaning that R499 rain debited will not be paid I'm going to change my bank and move my debit orders if this is not resolved