As the competition in the online travel industry intensifies domestically as well as internationally, enticing travelers to purchase travel packages by argument quality and source credibility through the channels such as mobile apps and web sites has already matured. As such, this study identifies the status of global online travel agencies that dominate accommodation reservation platforms in the global travel market, including Korea. To revitalize domestic online travel agencies, the current research examined the relationships among the variables of Elaboration Likelihood Model(ELM), Congruity Theory(CT) and Post Acceptance Model(PAM). A total of 348 responses were collected by an online survey from the male and female adults who had prior experiences of hotel booking services from online travel agencies. Findings suggest that perceived usefulness mediates the relationship between functional congruity and source credibility and brand attachment, customer satisfaction, and continue use intention. Also, self-image congruity was found to fully mediates the effect the relationship between intention to use continuously and brand attachment. In other words, online travel agencies have a great impact on the intention of continuous use, depending on the degree of perceived usefulness and the degree of brand attachment. This study expanded the research area by applying the ELM, CT, and Extended PAM to the existing knowledge on the relationship between online travel agency's argument quality and source credibility perceived usefulness. It is expected that the detailed key facilitating variables and constraints of online travel agencies obtained through this research will revitalize domestic online travel agencies and provide the factor to increase customers intention to use continuously.