Phone help

I'm in a bit of a predicament

My current phone has some problems. When its in my pocket it seems to absorb heat and only a few hours after unplugging and not using it, it dies.
But when i leave it out on my floor for two days, it will last
So i came to the conclusion that its not the battery, its just the phone that over heats

Now I'm up for an upgrade with Verizon, but my parents don't want any new contracts
Me and my brother both want iphones, and although i doubt it will happen, my parents don't want to get stuck with a contract

I can either pay $50 to "extend" my warranty and just get a replacement phone, or i can go on ebay or to a friend and get a phone there and just switch it out.

So what do i do? i don't want to be stuck with this same phone for another year. But i can't sign into a contract in case we switch. But we probably won't switch, so i want to get a new phone...


ehhhhhhhhhhhh