Cheech Chi comments

FYI, if a Japanese carrier tells you they can't unlock an older generation iPhone that is only partially true. A Genius at the Apple store explained this to me. Apple can but only with the carrier's permission. When you take the phone to the Genius bar, a Genius checks the "Lock status" of the phone. If its set to "Locked", they can't do anything. If its set to "unlocked," then they have procedure that can unlock the phone. (it pings the server first to make sure the status is set to unlocked.) Apple can't CHANGE the status, the CARRIER CAN.

Note; usually if the carrier unlocks the status for you, all you have to do is wait a few hours and then restart the phone. Sometimes you have hard reset (erase everything).

However, if the law doesn't force them to unlock phones that were purchased before May 1st 2015, the carrier will probably tell you "sorry we can't do older iPhones" just cuz 1) the person you're talking to doesn't know how 2) easier to blow you off 3) they have no incentive because they think you're gonna leave their network once you do that anyway.