I am afraid that you are posting to the wrong place. This forum is for RingCentral developers only. You can post here if you have questions during developing apps with RingCentral.
It seems that you are a RingCentral Outlook plugin user. You should contact the customer service instead. https://support.ringcentral.com/contact-support.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:
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