Upgrading to iPhone 4 for verizon?

[Ryan]

I currently have a piece of junk phone, It's some little messaging phone. I currently have my phone on an unlimited talk and text plan. I am scheduled for an upgrade in March, So i was wondering if i could use my upgrade to get the iPhone 4 for my friend who has a smartphone plan. Would it work? And would I have to pay full retail for the Iphone? Thanks