Lol i think the person is just calling and not wanting to work, just calling and leaving no messages or voicemails. If i was doing their job i would do the same thing. :)
It's some stupid sweepstakes or some crap, that wants you to enter. Though I'm sure its a gimmick. They are probably after some personal information. They do give you an option to cancel and have them stop calling your number.
They are trying to get you to subscribe to a buyers club. If you call back - you stay on the line press 5, then listen to another message then press 2 to opt out. Worth it to me to take care of. I get way too many of these types of calls.