Early unauthorised debit order

I am not happy. Every month the debit order for my life and disability insurance get deducted before the agreed date of Debit. This month ( January 2019) you thought it to be a good idea to debit me on the 18th of January. I phoned and was told it will be taken up and then my account will be refunded. Still nothing. Please advise me on how I can cancel my policies. As a company that thinks it is ok to debit someone without taking into account the AGREED debit date is a breech of contract and I do not trust you anymore