How to open a ticket to determine the cause of bad call quality with Twilio.

Also be sure to run:

Interpreting Call Error Codes

If you're having issues with call quality during a call, you'll likely see an error code appear at the top of your HighLevel dashboard. You can view the meaning of each error code here.

The most common errors are: 

high-rtt - Round-trip-time (RTT) is the measure of latency in the network. Higher latency can result in perceptible delays in audio.

high-jitter - Jitter is the measure of variability at which packets arrive at the SDK sensors. High jitter can result in audio quality problems on the call, such as crackling and choppy audio.

high-packet-loss - Packet loss is measured as the percentage of packets that were sent but not received at the SDK sensors. High packet loss can result in choppy audio or a dropped call.