Debiting on the 24th, and not the 25th.

I have been trying for months to get Direct Axis to change my debit order date from the 25th to the 26 or 27th. When the 25th falls on a Saturday, Direct Axis insists on trying to debit on the 24th when my account balance is to low for the transaction to be successful, as I get paid on the 25th, irrespective of what day it falls on. I have gone through the process of changing the debit date twice, and the 24th July 2015 was the third time they have attempted to withdraw before I am paid. It seems they are totally unwilling to change the debit date, even though I have followed the procedure to change it twice now. Every time this happens I incur bank penalties. I have an exemplary credit history and I feel they are treating me like a defaulting customer. I feel helpless as my company is unwilling to pay me on the 24th, and I don't see why I should arrange for the money to be in the account when they can debit on the 25th, like all other organisations are prepared to conduct their business.