As competition in the market around the world intensifies, the bargaining power of buyers increases against the sellers or service providers. With more and more firms in the market, buyers can enjoy the benefits of competition such as lower prices, higher quality goods, and/or better services. Some of the most annoying problems regarding migratory customers are ever increasing bargaining power of customers, word-of-mouth, and strategies of competitors. In this study, we develop a simple game model. As firms from outside a specific industry or country may enter the market without tough barriers, the bargaining power of selling firms or service providers has ever decreased drastically. Thus, competition among firms has become very severe in various markets, especially in a saturated market with undifferentiated and homogeneous products or services, resulting in poor market performances even with more intensified marketing activities. Recently, due to high marketing costs many firms in the saturated markets have shifted their strategic focus to keeping their current customers from getting new customers. Thus, customer relationship management has become the critical factor for success in the market. Migratory customers are a typical type of customers, harassing marketing managers of firms. They are highly likely to migrate to a new firm for somewhat better benefits or conditions among many reasons. The more troublesome ones are high-profile or highly profitable customers who are to migrate, although it is very difficult to figure out such migratory customers in advance. The strategic stance taken by firms against migratory customers affects the cash flows of the firms in the current period and following periods. Some customers who generate sufficiently profitable cash flows for the firms in the market might threat or ask the firms for better contract conditions and change the firms often. In this paper, we examine the effects of strategies of firms, and the number of firms in the market on their profits. In the simple set-up, firms are in the dilemma of not rejecting the request of their high-profile customers for better contract conditions such as lower prices as long as there exist profits from them. We define the migratory customers as those who migrate around in the market for a firm accepting their opportunistic proposal for renegotiations without disclosing their true type of opportunistic behaviors. We first develop a two-period model in which firms enjoy profits from their customers in the initial stage, until some of their profitable customers ask for better contract conditions at the end. Firms make decisions depending on their long-term payoffs expected as a whole as to the different levels of wordof- mouth set exogenously. Firms are better off to accept the threat of ‘leave or take’ by a single customer asking for a new contract in the single period game as long as the firm can enjoy profits from the customer. With the effect of word-of-mouth and competitors in the market, the decision of firms’ accepting or rejecting migratory customers is not so simple as usual widely -known marketing slogans like ‘Customers are kings.’ We rather resort to the old saying of ‘Business is business’ in dealing with such migratory customers. The optimal decision making varies as to different strategies of the competing firms, cash flows from the customers, discount rate, the numbers of periods and competing firms, the level of word-of-mouth, the distribution of customer profiles, etc to name a few. With the game theoretic model seeking for Nash equilibrium, we focus our study on the unstable situations where firms try to accept migratory customers for short term profits even though such measures are suboptimal in the long run depending on the proportion of migratory customers. We extend our prototype model for infinite periods and N number of firms in the market for a generalized model.