I purposely never answered this call.  Caller ID said "unkown" and no message was left.

called and hung up when the answering machine answered

A rep asked for a Mr or Mrs (knew my last name) and they were offering Carribean Vacations.   Told them I don't even own a passport and to take me off their list.    The woman was polite and let me say goodbye.   I realized it was a Canadian number, and that they obviously were complying with the Do Not Call List, so I called them back but doesn't ring, just answers and hangs up a fraction of a second later.

called and hung up when the answering machine answered. Unknown number shows on call display. Called back again right away and same thing.