Jay has a feature phone and he wants to change carriers without having to buy a new phone. He's on Verizon, which is a CDMA carrier at the moment, which means the only carrier Jay could move to is Sprint. Then he'd still need to have the phone unlocked. He can keep his number because the FCC has mandated that users can move (or port) their number over so they don't lose it.
Every carrier has "zero dollar" phones. So it's going to be a lot easier to just go to any carrier he wants and use a phone they offer for free. He could even go month to month. Leo recommends TING or US Cellular.