RoBo caller said my MasterCard is locked. I don't have a MC but called the number back to find out who would answer. I stayed on the line for about 2 min. Never got a person on the phone there was only a recorded message: "your call is very important to us, please stay on the line and you will be with the next available agent".
Called me at 1:11am. A recording said my MasterCard had been locked and to press one to speak to someone to unlock it. I've never had a MasterCard so immediately knew it was legit and hung up.