This is fun, but from what I understood, the purpose of those random sms is to "warm up the number", so the best course of action is to either ignore them or reply STOP.
https://www.federalregister.gov/documents/2024/01/26/2023-28...
https://consumer.ftc.gov/articles/how-recognize-and-report-s...
I like how one of those was called the CAN-SPAM act. Others have been similar.
Slowly, as more people opt into it, we can make it opt out, and then get rid of the old protocol completely. If some countries don't want to adopt the new protocol, well tough luck at that point but I think it is fundamental for us to be able to trust caller ID before we can do anything else.