You can set an unsubscribe text message here. If a contact wants to opt out of your promotional SMS, then they need to type this message as a reply.
Furthermore, if you want to disable click tracking for all the SMS broadcasts and automations, you can do that from here.
Click tracking adds a special variable to the URL that leads to increasing the character limit of an SMS. By enabling this option, it'll reduce the character limit.
Once done, click on Save Settings and you are good to go!