program Pre-Paid Android to be used on Post-Paid (contracted) account????

So I have a Prepaid Samsung Galaxy Legend, that I got from my friend for free to replace my old phone until I have my upgrade and we both didn't know the dang thing was PREPAID. So frustrating! Anyway, I'm starting to get the hang of rooting and flashing roms and what not (probably sounds amateur lol...), and would like to ask the pros out there if it is possible to Root, maybe flash a custom rom, or reprogram the phone to be read as Post-Paid so that I can use it on my post-paid account with Verizon. The phone is great, and I haven't done much research on the ROMS but I bet there might be some cool ones out there. If anyone at all could point me in the right direction or even be willing to build something (I'm not that good yet), you know as a little challenge or something. I would be more than happy to donate what you think is fair and brag you up! Let me know!! Thanks again and sorry if I'm such a newbie and this is old news.....Peace.