To fully block all promotional messages, send 3311 to 900, and to unblock send 3322 to 900.
To block promotional messages from a certain sender ID, send the sender ID or the sending number to 801001.
To unblock promotional messages from a certain sender, send the sender ID or the sending number to 801002.
For more details on your block list: send blank message to 801001.
To unblock all blocked IDs: send DELALL to 801002.