debit order date not followed as per contract

I have just received a text from telkom staying that my account will be debited on the 15th July. This is not the date that was selected in my contract or confirmed by your consultant!!! It is supposed to be the last day of the month for a reason. I went into my local branch where I was told that nothing can be done. If you are not going to follow the signed contract, please terminate it immediately And do not attempt to debit my account on the 15th!