Generally, you can contact any SMS recipients through a Proactive SMS Campaign. Remember that Gladly will create a Customer Profile for recipients without an existing one.
Customers can opt-out of receiving SMSes, which include SMS Campaigns and receiving support via SMS. If they reply to an SMS Campaign with an opt-out keyword, the SMS tag on their Customer Profile is removed, and they’ll receive a message that they have been opted-out. This also prevents Agents from sending the Customer any SMSes in the future unless the Customer reaches out to you first and replies “Start” or “Unstop” on the same SMS thread/phone number they unsubscribed from.