In every campaign, you should include a way for the consumer to opt out of future campaigns. It is different from traditional SMS opt-out mechanisms like 'text stop to 12345' but gives the respondent a way to opt out.
The opt-out is available via the campaign designer. The opt-out widget is present in both the notification and survey wizards. It looks like the following.
Adding an opt-out is easy. Simply click the 'Opt-out' widget on the right-hand side. This will cause the widget to fly into the phone. That's it. Make sure to save.
By default when you upload contacts to a group the 'opt-out' parameter is FALSE meaning they will receive the text/email messages.
When a consumer receives a message and they press the opt-out button and confirm they want to opt-out, the parameter of the contact will turn to 'TRUE'.
If you send to that group again those users that have opted out will not receive messages. You do not have permission to edit the opt-out parameter in the contact section unless directly instructed by the consumer.