In industries such as the mobile telecommunications market, where the business is subscriber-based and customer churn directly translates into competitors' customer base, preventing customer defection and inducing continued service usage significantly impacts mobile telecommunications operators' performance. Accordingly, numerous studies have been conducted to understand customers' service continuance behavior, but the provision of an integrated theoretical framework has been lacking. This study explains continuance usage using a dual model consisting of a volition-based mechanism and a constraint-based mechanism, based on the factors influencing continued use. Furthermore, by adding alternative operator attractiveness to the constraint-based mechanism, this study provides an integrated model that can explain not only the customer's relationship with the current operator but also their perceptions of alternative operators who could become potential service providers. Testing the model on young adults with high mobile telecommunications involvement, the results revealed that under the volition-based mechanism, customers' expectation confirmation and satisfaction were linked to continuance usage intention. Under the constraint-based mechanism, perceived switching costs were found to have a binding force that keeps customers using the current operator's services. However, this binding force was found to be weakened by alternative operator attractiveness—measured in terms of perceived price attractiveness, handset quality attractiveness, service quality attractiveness, and subscription ease attractiveness—particularly by perceived price attractiveness and handset quality attractiveness.