Unauthorized Debit Order (December)

My debit order date is set for the 25 & 28th of each month as stated in my contract when i app**** for my loan. But this month you debit my account on the 15th December. when i called i was told that Standard Bank decided to do it earlier because people do not pay in time for the month of December. I get paid on the 25th of each month. It doesn't matter whether it is December or not. All funds in my account are gone and i need to use the money for the kids. I want my money today. This was not authorized by me and it is very unprofessional and leaving us penny-less. I DONT CARE IF IT IS DECEMBER AND WANT TO DEBIT EARLY ,STICK TO THE AGREEMENT WHICH WAS SIGNED. I HAVE NO FUND AVAILABLE THANKS TO STANDARD BANK, REMEMBER NOT EVERYONE GETS PAID EARLY IN DECEMBER.