2018 ruling: https://www.reuters.com/article/us-usa-fcc-texts/fcc-affirms-that-wireless-carriers-can-block-unwanted-text-messages-idUSKBN1OB2FP You can find plenty of evidence of carriers blocking messages they don't want sent, just search. Lately it's mostly blocked for "Covid misinformation" but there are examples going back to 2010 or so. SMS is not anything like a secure channel. Use something more modern if you want privacy or censorship resistance.