"It was weird because people would call and then they wouldn't say anything. Maybe they were shocked or something.... You'd say, 'Hello...' and then it would just be silence or heavy panting or weird sexual noises - and then they'd hang up. It was bizarre. And then I changed my number." Adam Levine on the strange calls he received after prankster Blake Shelton gave out his friend's cellphone number during a recent live broadcast of U.S. talent show The Voice.