These telemarketer computers call your number to see when you pick up the phone. They then sell this information to other telemarketers so they know when is the best time to call you. They have been calling me twice a day. When you call the number back you get a recording saying, "this phone number is not in service. Please check the number you are calling and try again." And then they change the phone number to another area code.  My suggestion is not to answer the calls at all.