Solution for me:
Microphone does not work during calls.
I am currently using Lenovo A7000a- Android version 5.0. I had the same problem for about 6 months. I installed many OTA updates, but none fixed it. During calls I could hear the other person, but they cant hear me. However, it worked fine for some time if i restarted my device. So every now and then, I had to restart my device. Also, everything was fine while placing skype calls or whatsapp calls or testing mic recordings. I knew it was a software glitch and the noise cancelling microphone was to blame.
I googled a lot, and scanned through different forums, nothing helped much. Like someone told that using the speakerphone would correct it, but it didnt worked either.I even rooted my device to alter the build prop to change the value of persist.audio.fluence, however, no such element was found in my build prop file
I did two things after doing a lot of research:
1. I cleared the data in Apps>All>Phone/Call
2. Disabled all the apps in Permission Control that had the permission to i)Record ii)Initiate Call iii)Initiate Multiple Party Calls iii)Write MMS (everything that could use your mic.. ofcourse except the system apps).
I am not sure what solved the problem. But now everything is fine with/without earphones with mic. PS: My Call Recording app may be causing this prob, but I am not sure.
My phone is working fine from the past two days...Thought to share my experience with everyone.
Hope that helps..