Early Tyme bank debit orders in December

I received an SMS informing me that they will debit my account on the 13th December for a loan repayment. Then I called the service centre informing them not to change my debit date as I don't get paid early in December. They say there's nothing that they can do to help me...now I am going to incur charges for a debit order that will obviously bounce...Not happy at all and that I must manually pay them when I have available fund. Me calling early doesn't help.