Just stop holding the phone so wieldy.
I have been practicing this all day, and I don't understand how some of you can hold the phone so awkwardly and unwieldily.
You can easily hold an iPhone with two or three fingers, which allows you better placement and maneuvering. This not only helps with the signal but also likely with the proximity sensor.
I just don't understand why anyone would hold the phone with a palm death grip wrapped around the phone be it right hand or left hand. it is awkward, uncomfortable, and unnecessary.