- Check that you have not muted your outgoing audio.
- Check if the issue is with a specific number on outgoing or incoming calls.
- Record an audio clip, and play the recording. If you can hear the recording, the issue is not with your microphone. To record a clip, use the pre-installed Voice rec. app.
- If possible, try a wired headset.
If the problem persists, remove the battery, and put it back into the phone. Switch your phone on.