Purchased used iPhone from Amazon. Turned out to be a Japanese iPhone MKUF2J//A.... It seems to work fine on my carrier AT&T. It also included AppleCare+ which I wasn't expecting. I got it for a good price considering the condition and the AppleCare+ which is for the next 21 months. I can either return it or keep it. Should I be concerned about anything? This isn't from a individual but from a large company that sells on Amazon so no way to get in contact with the direct original owner.