It's been said on here before (recently, like in the last week) from VM staff that VM don't compensate you to "pay off" your existing provider, so tread carefully.
It may be that they are simply offering a discount from the standard rates, and you can get these from lots of comparison sites on the web too. Not sure if I'm allowed to state which but I'm sure if you are here, you can use a web browser and search engine 🙂
Note that some sites offer higher monthly charges and more cashback, whilst others do it the other way around.