Ridiculous debit orders on incorrect contractual dates

Every month when the 25th of the month is on a Saturday, Direct Axis deducts debit orders on the friday, 24th irrespective of when your payday is. I have written to them on several occasions to inform them that I don't get paid on the 25th but get paid on the 26th. If the 26th is on a sunday, I get paid on monday 27th but these people keep on debiting on the 24th!. Every time they do this, I incur bank charges and my account will be in the red because of being overdrawn. No one listens I don't know what to do anymore. This is just ridiculous!