I'm in China and I occasionally get spam SMS messages. Most of them ends in a sentence that says this or something else alike.
Reply T to unsubscribe.
(T is the leading letter in Chinese word "unsubscribe")
According to other answers and questions about spam emails on this site, it's better to ignore them (and optionally reply T to those identified, trusted message sources like my ISP).
Is it really safer to ignore and mark as spam/junk, or reply something hoping I'll get unsubscribed from 'em?