Er. Sort of? Depends on what exactly you mean. Wifi (as most people mean it) isn't really a separate service... you just connect a wireless router to your modem and then the router will broadcast wirelessly. Voila, you have wifi. We currently provide single-computer modems, not wireless routers, but you can just go to the store and buy a wireless router for fifty bucks and use it with your existing service. So no, we don't sell wifi routers... but you can buy a wifi router from a store and then use it with our service at no additional cost.
That is, of course, assuming you mean a local wifi for your home network. If you're talking about a wireless connection that you'd use away from home (like to connect your iPhone or Android to while you're off on a trip)... then that's a separate wireless data plan, and those are usually tied in directly to the voice plan for the iPhone/Android/etc. anyways. We don't have anything to do with that (just in case that's what you were talking about).
