Blocked Contacts

I have a few iphones signed in under the same icloud. Only one of them has cellular data (my main phone) and on that phone i blocked a contact ( he also has an iphone) After i blocked him, one of my other phones beeped and it was texts from the number I had just blocked (they didn’t go through on my main phone, just came through on my old devices)

Also the texts came in as iMessages, under the actual phone number I blocked not the contacts Apple ID and so I called him and asked him what color they were and he the messages he sent were blue and said delivered.

So, my question is how am I still getting text messages from a contact I blocked? And how am I getting them just on my other phone, my old phone, the one that does not have cellular data?