Early Debits

In December, MFC debited my account early without notice. As this was before the due date I had no money in that account and it bounced. The reason given was that other people had defaulted on their payments. Not sure why that's my problem. If I was notified I would have ensured there was money in that account. However, as a result of their actions, which were in violation of our contract, I was charged R150 for the failed DO and my credit record was affected. Today, I received notification that the money will be debited early again this month. No option to say no, just a notification that it will happen. This is unacceptable as it is not the date agreed on contractually. Shouldn't both parties to a contract be held to the terms of the contract?