iPhone 5 screen does not activate after a phone call One of the permanent features on an iPhone turns off the screen (display and the touch receptors) when during a phone call you press the screen against your ears and cheek. The screen would almost instantaneously turn itself completely "on" when the phone would move away from the cheek and ears.

This at least was the case before iPhone 5. On my iPhone 5, the screen sometimes does not turn off or turn back on. I can confirm that iOS6 has nothing to do with this --my old iPhone 3GS on iOS6 does not face this problem.

Following the recommendations of this post, I went to the Apple Store but they just replaced my iPhone 5 when I demo'd the problem to them. The new iPhone 5 unfortunately has the same problem --even with factory settings.

Does anyone know of a way to solve this problem or am I just unlucky to get two defective iPhone 5s in a row and should try my luck again?

P.S.:- I am not using any cases, covers, screen coats or any other accessories.
Sadly - you might need to take it back. The proximity sensor is a small part and if it doesn't sense that your head/ear/face has moved away from the receiver slot - the screen will not light up again.

You can save yourself a trip by backing it up (yet again) and restoring it in iTunes  - but it seems you have already ruled that out.

One thing I have seen in practice is that some people's ears have openings large enough for the proximity sensor to sense the space when the phone is pressed next to their ear as actually being away from an object.

Again, it's often best to lie the phone flat on the table and call some sort of automated help system and use a pencil eraser or your finger to test how and where your particular sensor is sensitive. Once you've spent a handful of minutes discovering how narrow the beam is and exactly how many mm the range is to engage and disengage the sensor, can you take it in for service and know the unit you have is working according to specifications.