Organizations have the ability to signup to send SMS messages to Guests. If this is a feature you're interested in please reach out to your Implementation Manager/CSM.
When a Guest Opts Out from receiving SMS messages they have the option to Subscribe to receive SMS messages. There are several responses a Guest can respond with to Subscribe to receive SMS, these responses are mandatory to comply with CTIA guidelines for US short code programs.
To see the HELP Responses review the article below:
To see the STOP/Unsubscribe Responses review the article below:
To confirm a Guest has been unsubscribed from SMS messages review the article below: