It’s the Survey SCAM. Call back gets, "Thanks for calling. The survey you were called for is now finished." This robo "survey" is how the telemaggots get around the DNC regulations. There is no survey just some nonsense questions. You'll be offered a free something for completing the survey then asked for you credit card number. It's a SCAM. Block it.
http://www.ag.state.mn.us/consumer/Publications/SurveyScams.asp
Called my cell at 9.30am. Didn't pick up and they left no message. Then they called my work phone twice at noon. Again, no message left. Pretty sure it's spam.