Microphone not working iPad 7th Gen (10.2)

Whenever I am in a call, my audience cannot hear me. I tried recording my voice as well in the recorder but it did not record anything. However, when I am using earphones, my audience can hear me clearly. I tried fixing the main settings, apps, plugging and unplugging the earphones and restarting it too but nothing worked.

May I know how can I fix this problem?