They never leave a message, but continue to harass by making more calls. STOP!!!

these guys are great, they gave me all sorts of free stuff!
nah, just kidding, they [***] call day and night, and when i finaly answer they [***] hang up on me!
i bet they just get paid by the call , not the answer!
if i get the address i'm going over there and calling the number, then i'm gonna [***] smack who picks up first!

I got a voice message on my phone from some lady talking about some kind of investigation but she wasn't being specific about it, so it's obviously a scammer.

a survey

This number called my cell.  I called back, but an operator answered.