Received a call. No one on the other end. Call ended after maybe 15 seconds. Did not sound like there was anyone on the other end. I suspect computer generated.
It's a robot phone number harvester. It keeps dialing until it confirms a human voice then hangs up. Calling the number back instantly generates an automated message, "to be removed from our list, press any key and allow up to 24hrs to be removed," which is a fake-out. Real opt-outs read your number back to you to confirm; I called this one from a blocked number, so there's no way it had a number to remove.