Absa Homeloan debit order date

Kindly note that we have a Homeloan with ABsa,the agreed debit order date is on the 25th of everymonth,however the have a tendency of debiting when they feel like sometimes after the 1st when money is no longer available.We went to the bank and they agreed to sort it out,apparently it is still continuing.Kindly assist.MM Mthembu ***