Hi @Martha Almeida looks like this needs more information and investigation, can you please open a service ticket - https://developers.ringcentral.com/support/create-case for your support team and provide more information like your 'Production Number, which SMS API you were using and your application client ID" ?
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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