We have received reports from our users that they are not able to opt out of mobile communications on their own if they have already opt'd in previously. For example, if I sign a petition and check the box to "Send me text message updates" (or Email Updates) and proceed to sign the petition. In the control panel I am fully opt'd in to receive Mobile communication (or email communication). If I then go to another page and leave the box "Send me text message updates" unchecked (because I want to now opt out of mobile communication), my opt-in status stays active and I will continue to receive mobile communications (even though I attempted to opt-out).
For email communications, you can get around this by using the /unsubscribe page, but there is no such page for mobile communications. Thus, the only way to opt-out of mobile communications is by doing so on the first ever addition to the database (unchecking the box when you first sign up) or to reach out to a control panel user to opt-out your profile for you.
Thanks Alex! In the meantime people will be opted out when they reply to a text with one of the following.