My debit order not going off on the date I have aranged

I've change my bank account to fnb so I also asked for MFC to please change my debit order to the 1st of every month. I noticed that my de it order goes off every 27th of each month. I left this as is because I get paid on the 25th buy now I received a sms from MFC wich says that my debit order will go off on the 23rd of desember. How is it possible for you to just change the date as you like? Who will pay the banking fees if there is no money in my banking acoount? Please correct this as soon as possible because I will NOT be held responsoble this. I need my debit order to go off every 1st of each month!