Unauthorized contract sign-up

I spoke to an consolultant around a month ago about taking up LTE. I specifically said I want it month to month, the consultant said to me that's fine I just won't get a modem, which is agreed to. I now learn that I have been enrolled into a 24 month contract without my knowledge or consent. I am now being told that if I wish to cancel this I will incur charges as I am canceling before the 24 Monts.