Wrong debit date and they want to suspend .....

My arrangement with Cell C since the beginning 7 years ago was always on the 1st for my 2 numbers (have 3). Now this month they submitted the debit order on the 31st. It did not go through as our money is only available on the first. Now they dare to send me a sms that my lines will be suspended due to this. If only they keep to the agreement of the 1st of every month as per contract we will not have this argument. There is always that one thing that they do not do and this influence you (Me) the consumer and influence my credit score negatively. Will they set the record straight? We still have to see...don't think so. Why should they care?