We have two iPhone 4S. Mine has signal all the time, my wife's phone shows 'No Service'. This has been going on for the past week or so. When I switch on airplane mode on both phones, wait 10 seconds, switch back off, mine goes to Searching and finds the carrier within a short time, my wife's phone basically goes to "No Service" a second or two after I switch off airplane mode. We put the phones on the desk next to each other for the tests, but sometimes also at different places in the room. Not happy at all. Admittedly the signal strength in our place is somewhat weak, but two identical phones should have the same reception quality if I am not wrong (we are living on the 41st floor in a Hong Kong highrise, but apparently the two antennas of our cell are far away). One of the phones is almost three weeks 64GB black and loaded with apps, the other one is 16GB white and a week or so old. Not that this would make any difference. Both of the same iOS version (5.0.1) and the same carrier version etc. Outside the 'No Service' phone works fine, so going to Apple will be difficult for a demonstration unless they send somebody to our home. I am kind of lost and clearly unhappy about this. I worked hard to convince my wife on an iPhone 4S to replace her HTC. And now that. Any pointers what we could do?