Blacklist contact management does not work.

Whitelist does.

Perhaps reputation-based / fee-based systems as well, where an origin number (or network) has a given reputation, puts forth a bond against abuse claims, and pays a sizeable penalty for each message after the first (or perhaps some n number of claims) on which an abuse claims is placed.

This is effectively the Metafilter mechanism, in which participants pay $5 for an account. Payment mechanisms are flexible, third parties may sponsor accounts, etc. On abuse that fee is forfeit. Casual activity is unlikely to trigger this. Malicious abuse gets expensive fast.

The reason for permitting a few freebies is to allow for services such as mailing lists or other mass distributions which might find themselves specifically targeted. What's being tested is the capacity to rapidly address any claim of unwanted contact and not repeat it, not to simply penalise each instance of abuse.

Again, the really bad spammers are generating millions or billions of messages per month. Not a few dozens or hundreds. Those are the key targets of countermeasures.

E.g., "FCC slaps $300M fine on “largest illegal robocall operation” it’s ever seen" (2023)

The fined party made "more than five billion robocalls to more than 500 million phone numbers during a three-month span in 2021".

<https://arstechnica.com/tech-policy/2023/08/fcc-slaps-300m-f...>