If your display is not turning off when you hold the phone to your ear, and you have white otter box case, follow these steps:
1. Remove iPhone from otter box case completely.
2. Get a black sharpie
3. Color the back side of the front of the otter box case all around the ear piece until it is black, this should not be visible when you put the iPhone back into the otterbox.
4. Put the iPhone back into the otterbox.
Try it out.