Had this little fella Samsung Bluetooth Headset mic not working for sometime and was about to dump it off, then I decided to reset it to factory settings. Miraculously it works.
Factory reset steps:
1. Turn off the device.
2. Hold down both volume keys and hold talk button for 5 seconds
3. Turn on the device
4. If pairing is needed, press talk button for 3 seconds. Start pairing process.