Thanks for the tip, but my issue is that people can't hear me when I don't use the headset. If I use a headset everything is fine. Sorry, if it wasn't clear in the original post, I updated it to make it more clear.
I seem to have an issue with my Mi4C where people can't hear me in call. I tested the microphone using the voice recorder and it works fine. Then I ran Hardware Tests:
1. Main mic speaker feedback test - Pass
2. Simulation call test - Fail but I can hear something if I make a really loud...