You have to turn it in when upgrading. you are leasing the phone. don't sell it
verizon isn't a lease
sprint's iphone for life is a lease. if you want to cancel iPhone for life on sprint you have to pay off all remaining lease payments plus buy the phone or surrender it.
in order to sell a edge device you need to do the following:
1. keep making mobile device payments or pay off the device , i think you should plan on paying off the device before selling it.
2. go to my verizon.com and transfer the line to another device. you do this by giving it a new MEID #
3. erasing the iPhone and remove it from your iCloud account
4. as an extra touch go to supportprofile.apple.com and remove the iPhone from your apple id. not necessary. but maybe its a good idea. so if someone calls apple care with your old serial # they won't automatically think they are talking to you
transferring the device to a new meid # on my verizon.com should unregister your device and allow you to sell your iPhone
moving the sim card instead of doing #2 might be all you need to do, but i felt like it was better to do #2 anyway. . i never had to actually type in a new MEID when i had my iPhone replaced under warranty. maybe this is no longer necessary and its only for older CDMA only devices and not needed for LTE. ask verizon
remove sim card when selling device.
