Blocked number still texting me

So I got a call from a phone number and then they texted me. I blocked them after that, then I blocked my caller ID and called to see if it was a specific person I know. This number is still blocked at this point. They texted me the next morning WHILE they were blocked?? It’s through text message, not iMessage and I double checked the blocked numbers in the ‘messages’ AND ‘phone’ in settings, the number I blocked is correct. How is this possible and how do I fix it??