Money withdrawn without my consent

Last month an amount of R 989 was deducted from my banking account at FNB. I queried it and was sent from pillar to post and when I finally got to speak to someone at a call centre I was told it was for my loan and that no future debits would be put through my account. When I queried this deduction as I have a statement from my Debt Councillor showing that the amount is paid to them each month, I was advised to hold on while a supervisor was contacted. After 15 minutes of holding on listening to mundane music, I put the phone down as I do not have time to hold on while they get their ducks in a row! This morning, again an amount of R162.98 was deducted from my account. Referrence - Student loan. I have sent an email to FNB demanding my money back as well as enclosing a copy of my debt councillor statement. What gives them the right to defy a court order and just debit money from my account! I have had it with FNB thinking they are the almighty bank that can do whatever they want!!!!! I do not want them to contact me telephonically, I want a response in writing - telephonic responses can never be disputed!