I just got the same nature of message from this number. It is very enticing isn't it. I called back that number from my home phone and the message said "the number that you called the user hasn't set up the voice mail yet.." I think we should stick to our guts and should avoid dealing with this type of invitation. I'm sure many would respond as asked...

Repeated calls from this number.

Got a text from this number promising a free iphone 5 for beta testing.  It sends you to a site that asks for personal information then quizzes you about whether you use various items that are clearly marketing questions even though they are phrased as a survey.  I quit before I got through all of the screens.