Here are a few steps:
Step 2:
Try to switch internet connection and try another call-
If you’re using a wifi network then switch to the mobile hotspot and vice-versa.
Step 3:
Try to use different headphones,earphones and check.
Step 4:
If the issue is not resolved then you can raise a ticket.
When to refer to this FAQ?
When a user complains about call quality.
When a user complains about one side voice/voice breaking / no audio/disturbance in voice or blank audio during the call.
Steps to Follow
Ask to change the switch from the dialer.
Ask the customer to check if the internet connection is stable or not.
check by changing the network.
Perform network Twilio test https://networktest.twilio.com/
Check if the headset is properly connected and ask to change handset and make a call again and try.
If the issue still persists after following all the above steps, ask for call samples which has call quality issue.
Raise a technical ticket with call samples with call sid with switch A/B detail.