Microphone problem on dialler.

[Android Central Question]

Whenever I call out on my Elephone M2 android phone using the Dialler app using hands-free, people always say they can hardly hear me. The microphone icon next to the hands-free speaker icon always has a cross through it as well and if I click on it it just makes a sudden noise but doesn't change. Why is this and how can I rectify it please?