What is if someone doesn’t want SMS from me anymore? How can they Unsubscribe/Opt-Out from my SMSs?

There is a “Subscriber Options” link at the bottom of every Campaign you send to your customers. If your user wants to unsubscribe/opt-out of your SMS, then they just need to click on this link and select the appropriate option to Opt-out or Update their existing information saved in your CRM.