It seems that you are still using Twilio trial account and Twilio trial accounts can only send messages to verified numbers (as the error is clearly mentioning that yours is a trial account). Did you verify the number you are trying to send the message?

From Twilio - "If you are using a Twilio Trial Account, you need to verify any non-Twilio phone numbers you wish to send SMS, Voice, or WhatsApp OTP messages."

Please follow this link.