phone calls daily

Credit Card Service phone scams have been calling me for months.  I called the Attorney Generals Office in our state and they said to not answer your phone.....let your answering machine get your calls.  If people don't leave a message then it isn't importtant.  Every time you pick up your phone it will cause them to keep calling.  They most likely are from out of the country, however the number that they have been using with me lately is a Colorado prefix.  It is 720 409 2532.  With computer programs they can be overseas and use U.S. numbers.  I haven't answered my phone when I see unknown numbers come up for 2 days, so I will see if not answering will take me off their list.