Chosen Solution
I bought this phone last week. I tried LINE and WhatsApp video call, and the other person can’t hear anything. Also I can’t use microphone when I use speaker on LINE calls. I checked all 3 microphones, it seems to work properly. I don’t know why this problem happens?
It seems your upper microphone is not working, how did you determine all three are working, did you try recording and playing a video with your front camera ? If you can record videos it should be working with net applications too. It might be just a software glitch, try first with a hard reset (power+home button pressed until reboot) and if that doesn’t work you may try a DFU restore if you can use a computer. Don’t forget to backup first as restore will wipe all data.
