The only way would be to unsubscribe but then you risk not getting freebies too...why not report the issue to a moderator as well as the community technical problems thread. Theres been all kinds of text issues with pm lately. They need to overhaul the system.
Is anyone getting a text 2-3 times a day announcing the lunar promotion ?
How can we get it to stop ?
If you're using a smartphoen, I would consider blocking (at least temporarily) blocking such messages. When using Android Messages, doing so does not prevent you from receiving the messages. You just won't be notified of them and the messages will be sent to an archive or spam folder. Remember to periodically check for these messages if they're important to you or to unblock the number after this promotion ends.