Are your AirPods fully charged? If not, try giving them a full charge and then test to see if this helps: Charge your AirPods with charging case and learn about battery life.
If not, you might try re-connecting your AirPods. First, tap Settings > Bluetooth. The tap the 'i' next to your AirPod and tap Forget This Device. The next step is to put your AirPods in your case and close it. Wait 15 seconds, and then open it. Next, press and hold the setup button on the back until you see an amber light followed by a white light. Then, re-pair the AirPods and test: Get help with your AirPods.
If you find the microphone audio is still breaking up or not working, try to get in touch with Apple using this link to look at your options: Contact Apple Support.