I'm considering picking up a nearly new iPhone 5 to tide me over until the 6 comes out next year, or maybe even the 6s. A lot of the units for sale are advertised as "unwanted upgrade" and say they are unlocked. When a network sends out an upgrade handset is it always genuinely unlocked or do some networks send out locked handsets, e.g. a cellophane sealed iPhone 5 handset sent out by O2 (as a random example) might have the handset locked to the O2 network? Or maybe the handset is unlocked but will lock to the first sim so if the seller opened the cellophane and tried out the handset briefly then it will be locked to O2 or whatever network was tried? If there are any issues with locked handset upgrades then does it vary from network to network and is it resolvable? If I buy on ebay then buyer protection is the ultimate solution I suppose, if the original ad clearly claimed that the phone was unlocked, but it would be a pain. Sometimes the seller's pictures show a readable IMEI number either on the back of the box or the back of the handset and I've already found one item for sale claiming to be unlocked where an IMEI search shows it as locked.