Difficulties interns of reversals. Within FNB

I can't be complaining about one thing every month I've double debited by Capitec from my FNB bank account but FNB makes it impossible for me to reverse the amount that I was double debited for. Please I need to have my money back into my account with immediate effect I can't call the creditor to do so because it obvious they will refer me back to my bank to reverse the amount.