When a phone rings, click on the character whose phone you think it is. If you're right, the character will answer the phone. Otherwise the character will surprise you. When all the characters in a scene have answered their phones, you'll move to the next level. You get 10 points for right answers and lose one point for wrong answers.
If you're playing at work and you don't want your boss to hear the game, choose silent mode, and the rings will be represented by visual patterns.