I am currently on 2 year contract with an Evo 3D. Would it possible to trade that in for an iPhone 4/4S and just have that on my account? And I understand that I will get 99$ for the Evo 3D from the Sprint Buyback program. Would it be possible to trade that in, and pay the rest to switch to an iPhone on my account?
Yeah, that would work, but in that scenario you would have to pay full price, minus the buyback, since you can't sign another contract yet. Our Account Services dept may, in select cases, be able to offer something called a buy up, where you pay to get out of the contract so that you can get the 2 year contract price. This offer is not available for all customers. Best of luck!
Next time I get a chance I'll go in to a Sprint store or call them to ask about that. I've seen a lot of posts on Craiglist about people going in to a Sprint store and switching phones with each other. Is that possibe if the ESN's and phones are currently in use, or would that only work on a phone with a currently clean ESN that is not in use?
It would have to be a clean ESN. It can't be currently on another account, or tied to a canceled account that has a remaining balance and it cannot be flagged as lost/stolen. So, before you buy it, you should call us with the ESN to check.