Debiting account before payday

I received a message from Telkom stating that they will debit my account on 24th. I called them to inquire as I only get paid on the 25th. The lady advises that it's their policy. I have 2 cell contracts with them and I advises them that there will not be sufficient funds available. They advises that I must do a manual payment after debit bounces. I advises that a returned debit order will affect my credit status. The lady advised that is Telkom policy. I asked for a superior but the supervisor refused to take the call.