You simply have no case!

It's quite clear you don't have case, and being rude wouldn't help you anything, just that simple! You can always go hire a lawyer -- we're living in a common law system -- and the lawyer can charge whatever he is pleased to do, and tells you "Regretfully you have no case!".

Well, this does not mean what they do is EXACTLY legal -- actually that's a little bit off from the PERFECT law (the "Do Not Call" Act), but that's a tiny offense, you wouldn't win a legal battle that actually bites anybody (a big fine, or send somebody to jail). Then, PRACTICALLY, "no case".