I am using ringcentral api for ringout in Dev sandbox. But unfortunately I am getting exception:
"message": "Forbidden", "errorCode": "InternationalProhibited"
If you are using Dev sandbox as you said in your question, that is free service for developers on Sandbox, and international calling is prohibited there.
check the link:
https://forums.developers.ringcentral.com/questions/136/api-ringout.html
Using the RingCentral Phone for Desktop, you can dial or receive test calls, send and receive test SMS or Fax messages in your sandbox environment.
Download RingCentral Phone for Desktop:
Tip: switch to the "sandbox mode" before logging in the app:
1 Person is following this question.