Mar 13, 2020 02:19 AM|Brando ZWZ|LINK
If you want to check the user's extension information, you should use the Microsoft graph to achieve your requirement. You could directly use the graph library, more details about how to use it, you could refer to below article.
Besides, I suggest you could also use the Microsoft graph api v1.0 to achieve your requirement, you could get the user's access token and send it to Microsoft graph api to get the user extension.
More details about how to do it, you could refer to this article.