I have a VZ iphone 6. In my location T-Mobile's coverage is very good so I plan on switching to I can save ~$25 a month. My question is I am ~12 months into my Verizon contract (not an edge plan) and want to use my phone on T-Mobile's network. In order for T-Mobile to pay off my VZ ETF do I simply need to turn in a phone? For example I can get a Trac phone on Amazon for $5. Do I also need to purchase a phone from T-Mobile, or can I just get their sim?