Same here. They called while I was in a meeting so I didn't answer. I tried to call back and it rings once and then it makes that beeping noise that normally means the line is being used.
Just got a call from that number on my cell but I did not answer and they did not leave a message. From other posts I realized that they have called me before because on that occasion I did answer and got that annoying ship's horn blowing. I can't block them on my provider but I just added the number to my "contacts" giving them the first name "don't" and the last name "answer-telemarketer". When they call again my caller I.D. will read "don't answer-telemarketer" and thats that.