Hello Laksar,
If only one mic works, make sure you don't currently have it set to only use one mic. In Settings > Bluetooth > Info button next to the AirPods name, make sure the "Microphone" option is currently set to Automatic.
If that is set correctly, try resetting the AirPods following the steps found in the resource you came to us from.
1. Put your AirPods in their charging case, and close the lid.
2. Wait 30 seconds.
3. Open the lid of your charging case, and put your AirPods in your ears.
4. Go to Settings > Bluetooth. Or go to Settings > [your AirPods].
• If your AirPods appear there as connected, tap the More Info button
next to your AirPods, tap Forget This Device, then tap again to confirm.
• If your AirPods don't appear there, continue to the next step.
5. Put your AirPods in their charging case, and keep the lid open.
6. Press and hold the setup button on the back of the case for about 15 seconds, until the status light on the front of the case flashes amber, then white.*
7. Reconnect your AirPods: With your AirPods in their charging case and the lid open, place your AirPods close to your iPhone or iPad. Follow the steps on your device's screen.
How to reset your AirPods and AirPods Pro
If the microphone still doesn't work after that, then you'll want to contact Apple for service options: Get Support
Cheers!