I've been on the national call register but still get these darn calls. Rule of thumb is I don't answer if I don't know the number - they can leave a message
I'm on the do not call registry and I still got a call from them, which I did not answer. I rec'd a call from them at my home and once we answered they continued to call every 3 minutes for 4 hours. We reported it to the phone co, they were going to investigate.
The do Not Call registry does not work. I've registered my same phone number on numerous occasions over the years and I get tons of spam calls. Don't waste your time.