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

You attempted to send an SMS from a Trial Account using an Alphanumeric Sender ID as the From parameter.

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.