If I want a new phone but my contract is not up, can I still get a new one for a lower price?

I want a new phone but my contract is not up and my phone has been giving problems ever since I bought it. I read about my current phone online (LG Rumor Touch) and everyone was saying that it sucks (Which it does). The phone I want to get was rated 5 or 4 stars for every site I checked (Samsung Epic 4G). For me to upgrade to that phone right now, it would cost me about $600. Is it possible that I could open a new account on my plan and just switch the numbers on my phone? (The old phone would still be used, just not for me). I want to keep my number, I have always had this number and I would prefer to keep it that way. So can someone please tell me if this is possible??