incorrect date of debit

Good day<br> <br> my bank has charged in unpaid debit order in dec on the 11th dec 2015 cause you guys try to debit on my account for wht I don't know.cause our agreement for a debit order is the 25th of each month<br> <br> you never send me an noticifation about changes<br> I will like you to pay back those charge into my account is R138 <br> if you want bank statement to see I can send