It is called an auto-dialer, also known as a robo-dialer. They use it and a computer to dial every number in a sequence, thereby hitting both listed and unlisted numbers
407-476-1141 called iPhone May 21, 2016 at 11:47 am. No caller ID. No message. Google says this is "Amy Morin Grand Caymen Ct Kissimmee Florida 407-476-5898". I do not know this person.
Got a call from this person to my cell phone. I didn't recognize the number so I didn't pick up and they didn't leave a message.
I'm on the FTC and State of FL Do Not Call List