Agreeing with other comment, having a quota to use would seem like a better thing. You could spread it over time or over multiple people. Chances are that after the first few noodz the target is going to block the number.
Even better yet : offer a fake/proxy number for people to get rid of the ones that do not take no for an answer and reply with only noodz ;)
Was also considering setting up a number that just displayed replies / posted to Twitter. Something you could hand out in a bar to someone pushy. Maybe auto reply with a few pieces of set text like this art project that messages Tinder matches with passages from Lady Chatterlys lover.
http://libbyheaney.co.uk/lady-chatterleys-tinderbot/
You’re right about the blocking. If someone is going to do it, it’s usually after the second message.
I didn’t handle that exception from Twilio when I first wrote it, so when the first person blocked texts it broke delivery for 2 days before I realised.