Be smart; don't answer calls from unfamiliar numbers. When you pick up, they know they have reached a working number. When you press "whatever" to be taken off their list, you are added to many more lists. If there is never an answer at your number, eventually your number goes to a dead file on that robo-caller list. Each time you pick up the phone, the calls will increase. A good call-blocker helps a lot, but there is no perfect solution. These folks are scammers, which in reality is just another word for criminals. Don't encourage them; just don't pick up the phone.