Telkom debit orders

I have had fairly good service from Telkom until this month, Dec 24. I have a data contract with Telkom of R234 per month, which goes off every 5th of the month. I have a signed an agreement with them. I had the choice of the 5th, 15th or end of the month which I found to work for me. All of a sudden, this month, they send me a sms that they are going to deduct the debit order on the 31st. I am a pensioner and only get my money on the 3rd of Dec. If they deduct the debit order there would be not enough money in my bank. I just want to know what happened to our legally signed agreement, which they are breaking now and who is going to pay the costs or fine at the bank and themselves? Have to mention that I am not the only one who are dissatisfied about the way they are handling this.