Competition between the mobile operators is becoming more based on subscriber's behavior. In order to improve mobile operator's competitiveness and customer value, several data mining technologies can be used. One of the most important data mining technologies is customer clustering and segmentation. This targeting practice has been proven manageable and effective for mobile telecommunications industry. Most telecommunications carriers cluster their mobile customers by billing system data. This paper discusses how to cluster mobile customers based on their call detail records and analyze their consumer behaviors. Finally, the subscribers categorized in four loyal groups and the strategy to apply has been suggested in a specific life cycle.