Sometimes a person I call on my Moto X can't hear me. Why?

[AC Question]

I have a Motorola Moto X. When I make a call I can always hear the person I'm calling but the person I called complains that my voice keeps fading in and out. My voice is normal and then gets very soft and they can't hear what I'm saying.

 

[dpham00]

If you are using a case then try to remove it