For a service company, the very important persons (VIPs) can provide more revenues than regular customers. Even the number of VIPs is few, once operators miss or late to response calls from a VIP, the possibility of losing the revenues is potentially huge. Therefore, if a company needs to satisfy VIP’s needs, the manager must provide two different services of call center. Because employee salary forms the most parts of costs, hiring many operators is not a good idea. Partial operators must be reserved to answer VIP’s calls. Because operators serve not only VIPs but also regular customers, how many operators can be reserved efficiently is important to discuss. To answer aforementioned questions, the opportunity costs must be considered to find the feasible reservation. In this study, the costs have be derived from the proposed queueing model to find the optimal operators’ reservations.