Microphone issues

[Nakah]

I have issues with the external microphone that comes with my head unit, I'm not using any extending cable.
The sound level is very low, people can barely hear my voice during calls.
I've also tested with a voice recording app and I got same result.
Finally I've tested the microphone in two different locations. The first one is at the same location as my car's oem microphone (under the roof, before the center mirror).
The second location is on top of the A Pillar.

Is there a way to adjust the microphone I settings ?