frequent unsolicited calls

My number has been called at least once a week during the past two years or more, with a female voice announcing: "It is imperative that you contact Card Member Services immediately....  I got a live person once, asked to be removed from the list and was hung up on.  When I called the number shown on my handset this morning, the message was "This mail box is full and cannot accept further calls."
How do I get rid of this troublesome call?