I had the above-reproduced SMS exchange with a bot from my horrible mobile phone carrier, Orange UK (now called "EE" after the high-pitched noise my incipient aneurysm makes whenever I have to deal with them, and because vowels) today. They have "good news" — I have been subscribed to "special offers" from "great brands" via SMS. And I can opt out. Except, surprise, it takes three weeks to process these opt-outs.
Not sure what I should do apropos of any "great brands" who pay Orange to spam me in the runup to Christmas: maybe just name-and-shame them here? Any other ideas?