Goosebumps: Dont Scream! (Hall of Horrors) (পেপারব্যাক)

Jack Harmon can't think of anything worse than getting picked on by the bullies at school, until he discovers an even bigger threat. After finding a cell phone, Jack begins to hear a strange voice on the other end. Jack keeps trying to make his new "friend" happy. Now everyone thinks Jack has lost his mind. How can he overcome an something that he can't see but is everywhere?