I typically report it to my carrier, I figure that they’ve got systems for controlling spam SMSs that go over their network the same way email providers have control over the email coming into their network. So, while reporting it to the FTC might help investigations, reporting it to the carrier might get those messages to stop. I also like to use VeroSMS to filter out messages, but my phone likes to offload the app (because I rarely need to open it), then I suddenly start getting more spam SMS messages.