[Lockdown]

So well I've been doing a bunch of research on here to figure out how to swap a phone I found on the ground to my current service. I'm on sprint, I used the ESN guide to swap the "newly found" phone to 0000000 and I have my current phone which is active and paid up which I want to use to swap over to the "newly found" phone. Question is how do I go about doing this?