[Q] LG G2 D800 doesn't work the mic topic

LG G2 doesn't work the mic, sometimes the mic works and others no. Now, the mic is dead. I installed differents roms and the problem is the same, I just can use the speaker, I thought I needed to change it, now I have a new flex in my LG G2 D800 (ATT) and it doesn't work, I read in other webpage that the mic is the same when the speaker is on or off, any suggest, help please, thanks for advance!