Is there cost per text message sent via API? If there is a link to this information please share.
You can check the details with the backend developer team by submitting a help ticket.
Meanwhile, you can refer this https://support.ringcentral.com/s/article/International-SMS?language=en_US
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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