will never stop calling you

I get a phone call from this number at least once a day, every day since about the middle of May 2010. They NEVER leave a message. One day I got tired of it and answered the call. After saying "Hello" twice with a pause in between there was complete silence. I hung up after 15 seconds (being fearful that I could be "charged by the minute".) Oh, and my phone number is on the National Do Not Call list. Apparently this company/person thinks they are special and don't have to obey the law.

Calls, never leaves a message, I don't want to call it back.