Uncer*****y of debit order

Since I started a contract with telkom, there has been problems and I'm tired of never knowing when and how much of a debit order will be taken from my account, when signing up I stated that I needed debit order to come off on the 25th, however over the last year it comes off on any other date besides the 25th as asked, by then I have paid other accounts so when they don't get their money my account with them is suspended, which is the case this week, so I transfured 485 that they should have taken on the 25th to get my account in again, now that I have transfured money into my account for other things, suddenly there is another amount of 1030 taken by telkom, but when I phone telkom customer care all I am told to do is wait 7 days or go to my bank .....