This study intends to explain smartphone usage behaviours in the post-adoption stage of information systems (IS) based on the IS continuance model, the technology acceptance model (TAM), and the competence of the users. In this study, smartphone usage is divided into two types: usage of the smartphone’s device functions and usage of applications. This is the first time this concept has been proposed and empirically tested. The results found strong predictors of user satisfaction (perceived usefulness and perceived ease of use) toward smartphone satisfaction and finally confirmed the influence of smartphone function use on smartphone app use. Finally, several important theoretical and practical implications and directions for future research based on limitations are suggested.