Computer-generated pre-recorded calls

I have been getting these calls for over a week. Call starts with "message from nom"--then offers 4 choices, 1 to accept call, other 3 are variously to send to voice mail, listen in to call, listen in to v mail. I tried sending to v mail(I don't have v mail but recording said I had 21 messages) and listening in--nothing just a beep. No way to get back to the originator--*69 doesn't work. Called phone co., nothing they could do, but at least there were no unusual charges on my bill. Often they will ring once, then stop. I think this is the National Organization for Marriage--there's a ballot issue regarding gay marriage on the CA ballot. I have to unplug my phone to stop the calls late at night. Anybody else have this experience. Thanks.