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Is it possible to use any of the company numbers as the caller id for any of the extensions? Essentially having a many-to-many relationship between extensions and company numbers? I have a requirement to choose an extensions from number on an SMS text based on the recipient (basically making it look like the message is coming from a local area code).

You can get a list of extensions by /restapi/v1.0/account/{accountId}/extension

Then check their numbers by /restapi/v1.0/account/{accountId}/extension/{extensionId}/phone-number.

Most likely you will find which extension owns the phone numbers.

Please reply if it doesn't work for you.

Numbers are assigned to extensions. You can check numbers of extension by /restapi/v1.0/account/{accountId}/extension/{extensionId}/phone-number


So you just authorize as that extension. And send sms from its assigned numbers.

I have a list of company numbers, they don't contain extension but when I send messages from RingCentral phone application then I can select one of them to make the output. How to authorize and send sms from this numbers.

I don't quite understand your question. But as far as I can tell, the sms is sent on behalf of the current logged-in user. You can specify the user's direct number as the "from" parameter and it should work.

Let me know if you have further questions.