Debiting on a date that was not approved.

Why would Nedbank try to debit my account on a Debi check on the 12th of December, I did not give them the order to do, I am incurring extra fees on my bank account because they are trying to debit multiple times, really putting the customers in a *** spot, if we didn't tell you when we getting paid in December it is because we don't know when, and you don't have the right to attempt to debit on a bogus date.