internet with MPT

hey guys, love the forum. I was hooking up a buddies Moto v3m with a cable tonight and hooked up to the internet using it as a modem. I then tried mine with a U.S. Cellular Moto v323i and somehow got connected to the internet myself. I immediately disconnected because i am wondering how in the world i got hooked up and if I am going to have to pay per data packet to do this? any help would be greatly appreciated