I received the three messages while I was reading the linked article! My messages came from "MobibroIQ". I did not respond.
I logged in to AT&T and launched a chat with Technical Support. I indicated in my description that I wanted to place a purchase block for 3rd party services billed to SMS. The entire exchange took about 10 minutes. I received an email for each line on my account indicating the purchase block had been activated and that a PIN code would be required for charges to apply. AT&T reported that the change could take up to 90 minutes to take effect. As I am typing this, I received a message from this "MobibroIQ" stating, "This msg confirms that u have discontinued and will no longer receive messages or charges for this service..."
Again, I did not reply "STOP."
I hope this solution is as painless and simple for you as it was for me.
EDIT: Follow up message from AT&T "To confirm, purchase blockers have been added to all lines and also checked your line #### & cancelled a subscript.charge for $9.99, will see credit next bill"
I logged in to AT&T and launched a chat with Technical Support. I indicated in my description that I wanted to place a purchase block for 3rd party services billed to SMS. The entire exchange took about 10 minutes. I received an email for each line on my account indicating the purchase block had been activated and that a PIN code would be required for charges to apply. AT&T reported that the change could take up to 90 minutes to take effect. As I am typing this, I received a message from this "MobibroIQ" stating, "This msg confirms that u have discontinued and will no longer receive messages or charges for this service..."
Again, I did not reply "STOP."
I hope this solution is as painless and simple for you as it was for me.
EDIT: Follow up message from AT&T "To confirm, purchase blockers have been added to all lines and also checked your line #### & cancelled a subscript.charge for $9.99, will see credit next bill"