No message left. Called other times earlier.  My number is listed on the "do not call" list so why do I receive unsolicited calls?

They're an Internet marketing company. You must have entered a contest

thanks.. I think it rings once and then boots off because I'm on the no call list

Received one call but they left no message.

Called me today while I was at work, of course no message.  Called back and a recording says they are internet marketing co and if I don't want to receive any more calls to leave my number clearly.  If that is truly the case then I applaud the way they handle it.  Most of the time when you call those numbers back they just hang up on you.