As the first point of contact between a company and the client, a customer service representative must have impeccable communication skills and conflict resolution abilities. Expect your interview to consist of a lot of role-play or "describe a time when..." questions that will test your ability to deal with irate clients, work well under pressure, and always keep a calm and professional composure.
What would you do if, on a product release day, 5 people were yelling at you, and trying to get your attention, all at once?
Take it one person at a time. Acknowledge all of the customers and assure them that you'll be right with them.