Whilst I have never used them, it looks like they are selling a service, not hosting. It therefore stands to reason that if you cancel their service you lose your mobile site.
Had a look for their terms and conditions and they do not mention anything about hosting, but refer to services:
"We provide various mobile website solutions for our customers, including but not limited to: our Site, mobile website conversion, mobile website creation, and mobile advertising solutions (collectively, the “Services”).. You may use the Services for your personal and business use or for internal business purpose in the organization that you represent, as long as you are in compliance with all provisions of this Agreement."
It is a little unclear, but it is easy to argue it in their favor based on that wording. Sucks for you though. But hey, you own the domain, so speak to a web developer before you cancel so they can see what you have and get you a new mobile site up an running. Or, get them to make you a responsive web design which I personally think are better anyway.