SPRINT!?!

So I am a college student and my family has what they call a "Grandfather Plan" at Sprint, which means anything we try and leave them because of their god awful service, customer service, and available cellphones, we end up staying because they give us an offer we can't refuse, over and over again. The two year plan is up and despite being able to get a new phone for really cheap there is nothing better then what I have now, Samsung MM-A920. The Instinct looks kind of nice, but you have to buy it's own separate 100 dollar unlimited plan and I really can't afford it, also I don't think the phone is worth it. I am not looking for a smartphone or a blackberry, just a nice cellphone that is an upgrade from mine, but there is nothing, after 2 years!?! I recently read on Engadget or Gizmodo that Sprint may be teaming up with SK Telecom which would be amazing, but I'm not going to hold my breath.

With no real light at the end of the tunnel for Sprint phones, my question is, can bring an Unlocked Verizon phone to Sprint and have it activated. As long as it has the right band there is no real reason they can't right? I realize they might not do it because they want you to buy theirs but is there something I can bring them saying "you have to because *insert reason*." I know there is a court case against Sprint in California forcing them to unlock their phones to use on other services if you leave (I live in Texas), but what if I come to them with a fancy Korean phone, is there a way I can make them accept it? Your help would be very appreciated, I have looked around and tried to find a straight answer but can't seem to find anything that gives a definite conclusion to my dilemma...

Call Sprint's customer service and ask them. That's what they're for.

I don't know how it works for you amerikkkunts, but I imagine sprint would be happy for you to use any fukken phone on their service.  And if not just make use of the grandfather "retentions" team - "I'd like to stay but you won't let me use my nice phone, these other people will"

tldr: yes, you should be able to use any phone on any network, but you might need to unlock it from the old network first.