Today Sprint has launched an insane limited-time deal for customers of its main competitor. If you are currently with Verizon and switch to Sprint, you will receive one year of unlimited service for free. That's unlimited talk, text, and data (though the usual throttling limits from Sprint's unlimited plan apply here too). The first catch is that you have to bring your own device, this offer doesn't include a phone. So you need to check if your current smartphone works on Sprint. And obviously if you're entangled in a device installment scheme at Verizon, you'll have to pay that handset...
Source: http://www.gsmarena.com/sprint_is_going_after_verizon_by_offering_free_unlimited_service_for_a_year_to_those_who_switch-news-25590.php