I have the iPhone 5. I was getting no data in certain areas. Instead of 4G or LTE it would just say AT&T with 5 bars. I went to the Apple store and they told me to replace the sim. I went to AT&T and replaced the sim and told me that it shouldn't go off of 4G. I replaced the sim and a day later I've had the same problem. It will switch from 4g to AT&T with no data. Is this a problem with the phone? The guy at AT&T said that it should never go off of data to AT&T, even if service is bad.