despite what Adam stated, which could be "true" by the book,
i was able to trade my phone for a used Evo, and over the phone--the seller and i swapped ESN's via Sprint rep Customer Service and he immediately enacted my warranty coverage (TEP $7/month) on the device.
you might get better luck going through the phone customer service than taking it into a store. as long as the warranty's showing active, even if the phone customer service enacted the warranty, the Store HAS to honor it. otherwise you're paying for a service that's not being honored--and you could prob BS your way to the manager about calling some news station and getting Sprint a horrible PR campaign in the area.
i bought a used one--noticed light leakage, and the HTC warranty is still able to be used since the manufacturer date is in the phone's data menu---that you can't access unless you know the dialer code.
i bought mine off of Craigslist--searchf or my contribution in the post about "buying evo off craigslist". it'll give you some things to look for and ask.
