Great question — answering as the UphillTech team:
To send SMS with trial twilio account TEST ACCOUNT SID and TEST AUTHTOKEN which is placed inside Phone Number > Tools > Test Credentials rather than ACCOUNT SID and AUTHTOKEN given by Console Dashboard > Account Summary. Because ACCOUNT SID and AUTHTOKEN is bind after you buy the twilio number and TEST ACCOUNT SID and TEST AUTHTOKEN is bind with +15005550006.
Full answer by Patel Maimit: https://stackoverflow.stackexchange.com/a/42361016 (CC BY-SA 4.0).
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