NO! NO! NO! Do NOT press any buttons when they call - just hang up. The message tells you that pressing a digit will remove you from their list, but what it actually does is confirm that a live person answered the phone, and you'll get more calls than ever! If you hang up, the robo-dialer should eventually drop your number from the database because it can't reach anyone.
Here it is Jan 2015 and am still getting calls from this #. I never answer, and they never leave a msg. Still very annoying!!!! I wonder, will they ever give up???!!!