Due to the increasing demand for smart phones, and the entry of new Mobile Virtual Network Operators (MVNOs), the mobile phone market is becoming active and severe competitive conditions. There are a few differences in relation to fees and phones among mobile phone services provided by three mobile-carriers: docomo, au and SoftBank. We analyzed the change of the preference for the mobile carriers and the mobile phones. This paper presents the results based on the original market research survey data. We classify customers in two segments: stable customers and unstable customers based on their contract intention with the current mobile-carrier. We show the features of two customer segments to understand the future demand of mobile carriers from the viewpoints of decision-making factors and satisfaction levels for mobile carriers.