I wonder if you should have unlocked it. We have a 4S. About 3 years ago I unlocked it from ATT for use on a trip to New Zealand. In NZ we bought a 30 day Voda SIM which has now long expired. However, it is still in the phone. We do not use the phone anymore (dead speaker and weak battery) but when we went on a trip recently I decided to use it with wi-fi only and it connects without issue. Of course it cannot find a carrier. I just checked and it still says its carrier is VodaNZ (makes me wonder if it is now locked to them, but it doesn't really matter since it will never be used as a phone again).