Have received several calls from these (I suspect telemarketers/scammers). Going to have to upgrade the phone so I can have more blocked call capacity, mine is full now. Likely a "robo dial" set up and they don't care how many times they call and you don't answer, they keep calling in the hopes that someone picks up. Personally I NEVER answer an unidentified caller and if it's important they can leave a message and I'd decide if I want to call back or not - no message = no call back.