Fibrestream refusing to cancel contract

I'm on the 25mb upload 25 mb download package for r499 with fibrestream. I received a email from fibrestream that they are migrating to mweb and I will be now charged R599 for the same package. I have requested to cancel with fibrestream as I have been with them over a year. They responded they can't cancel me as they in transition phase. I want my contract canceled immediately as this is ********. You cannot just decide you will not cancel a client's contract due to being in transition.