The issue is that I can't make calls to external phone numbers (I believe), for example when I place a call to +18002758777 (USPS), I can't hear anything on the audio channel and in the logs I can see "407 Proxy Authentication Required" websocket message from the SIP Transport. This happens for all the public phone numbers I find on the Internet. However, I can successfully call my other user.
Also, this doesn't happen when I call the phone number using the RingCentral app.
I couldn't find any information about this in the docs or in the Community.
Is this a matter of a configuration in the Admin Portal? I couldn't find any settings there that could be related to this issue.