21267: Alphanumeric Sender ID cannot be used as the 'From' number on trial accounts

You attempted to send an SMS, but the 'From' phone number you supplied cannot be used as an Alphanumeric Sender ID.

You are trying to use an Alphanumeric Sender ID on a Trial Account. Trial accounts cannot send from Alphanumeric Sender IDs.

If you are using an Alphanumeric Sender ID on a Trial Account, upgrade your account.