Only Accept Payment via Debit Order - LIES!

My salary gets paid into my bank account weekly. I have a Debit Order Agreement with Hollard Car Insurance, but sometimes due to the fact that I get paid weekly, there is no money in my account when Hollard deducts money (which is not always on the agreed date.) This results in me having to pay R100 every time the deduction is unsuccessful. I am just looking to cancel my debit order so I can pay via EFT for the month and no late deductions will be made, but when phoning them to ask how I can go about doing this, they tell me that they ONLY accept payment via Debit Order which is a blatant lie! I demand feedback/assistance - Because I am VERY close to cancelling my policy with them.