Your outbound calls may drop due to the following reasons: 

  1. Your account could be running low on credits. To add credits, go to Admin Settings >Account Settings > Plans and Billing > Phone Credits. Select the amount you want to add and click continue. For details, see How to add phone credits?

  2. Your microphone may be disabled. To enable, click on the lock icon in your URL address bar and select the allow option for the microphone. 

  3. Check if  0 appended after the country code or check if you have given a wrong country code while dialing the number.