Fake "survey" by a dynamic robot.  If you take the survey, which consists of inane questions like, "Would you buy an electric car?", you supposedly have consented to talking to a human later.  This gets them off the hook in case you are on the DNC list.  The entire call is a series of recorded messages, and what you hear is determined by what you say.  If you answer anything other than "yes" or "no", then the computer says, "Sorry to have bothered you today," and hangs up.