I am using ringcentral api for ringout in Dev sandbox. But unfortunately I am getting exception:
"message": "Forbidden", "errorCode": "InternationalProhibited"
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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
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