My friend has the same phone (LG G2 D802) as me and we were speaking on Viber and again without the speaker on it was echoing for the both of us. When we both turned on our speakers it started making a static like sound. Oddly enough when we turned off the speaker both the static sound and the echoing stopped. It was weird but i dont want to have to turn the speaker on off everytime and even when i do it doesnt work everytime.
My Device: LG G2 D802 (Android 4.4.2)