? About cell company's software & replacement phones

[pknoeber]

I live in SW KS and have a cell phone through United Wireless, which is a small regional company that has their own cell phone service. They are loosely affiliated w/ Sprint, but handle their own phones. I have a Hero that the ear speaker is crapping out on and they don't have a replacement. I would like to stay w/ the Hero...

Sooooo, when I ask them about getting one off ebay the answer is "Oh no, it won't have our software so it won't work." My question is this, and please remember I'm not a techie, why can't I get an unlocked phone and have them load their software?

Thanks!