Xfinity Mobile is only available to current Xfinity internet customers. Seriously. No ifs, ands, or buts. For those of you who don’t use Xfinity, check out the internet plans and see if it would make sense for your budget. If you’re already an Xfinity internet customer, you can easily sign up for Xfinity Mobile using the company’s website. There, you can log in to your Xfinity account and begin the process. The first step is choosing whether you want to buy a new phone or bring your current one. If you decide to buy a new phone (Xfinity is offering some killer deals on new phones, by the way) then you can find the one you want on the company’s website.