My vehicle is financed through Absa, the debit order date is agreed to be the last day of the month

My vehicle is financed through Absa, the debit order date is agreed to be the last day of the month. But Absa move the date sooner at their own decision without consultation with me. How do they know I will have funds available 3 days before the normal date the debit order should go off. Shame on you Absa.