called and hung up when the answering machine answered

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

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

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.