Sounds like you are going to have to send for a replacement. Does it sound that way on speaker too?
Looking through all the threads it's anything but a common issue
https://community.verizonwireless.com/community/droid/lg-g2
Good Luck 
I just got my LG G2- outside of 14 days.- I made the mistake of loving everything but I never made any voice calls cause i still had my old phone. Sounds Like its underwater. I tested calls to multiple phones and landlines. No one can understand me whether I make the call indoors or outdoors. Data and text is great, Software is funny but works well. Just terrible for calls though. I have to use a bluetooth headset to bypass the device to make clear calls. Anyone else have that problem? I hate the idea of having to go to refurb on warranty exchange if its not going to help the call quality issue.
Sounds like you are going to have to send for a replacement. Does it sound that way on speaker too?
Looking through all the threads it's anything but a common issue
https://community.verizonwireless.com/community/droid/lg-g2
Good Luck
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