Telkom Mobile is failing to change my monthly debit order dates

I was employed by a new organisation which pays on the 15th of each month. I then wanted to change my monthly debit order dates from the last day of the month to the 15th. I called Telkom mobile to change the monthly debit order date. I was told that the monthly debit order dates have been changed. To my surprise, the monthly debit order dates have not been changed. I called again and was told that they made a mistake and that they have changed them. Come month end the monthly debit order dates have not been changed. I then went to a Telkom Mobile store to request them to change the monthly debit order date. I was informed that they have changed them. Again, the debit order dates have not been changed. I have given up on Telkom mobile. I am just waiting for the contract to expire so that I can cancel it. It does not make sense why would Telkom mobile fail to do a simple task of changing debit order date.