Customer service has become a critical component of what a firm offers to its customers to generate customer value. Since there is a lack of strong conceptual foundation for the service economy, the science of service has become an important research topic. This dissertation contains two papers: a theoretical piece titled "ITEnabled Customer Service Systems: An Interdisciplinary Review and Integrated Framework" and an empirical piece titled "The Impact of a Portfolio of Service Delivery Systems: A Longitudinal Multi-Channel Approach." In the first paper, I used a structured methodology to review 757 articles drawn from information systems, marketing, and operations management literature; and then coded a subset of 142 articles into an integrated framework. The literature has identified six functionalities of customer service systems and the effect of technical/social attributes of the systems on these functionalities and customer value. This work makes two contributions. First, it organizes the interdisciplinary research around an integrative framework that should prove useful to both research and practice. Second, the review and analysis of the literature offers the basis for future research directions. I took one of the suggestions for future research that emerged from the theoretical piece and developed the empirical piece from it. I employed a longitudinal multi-channel approach base on an archival dataset of 389 hotels of a lodging chain to explain the conflicting results of the outstanding customer service systems literature. The results indicate that (1) the implementation of an IT-enabled incremental customer service channel leads to a disruption of the customer service process and that the true value of this investment does not surface until the new multi-channel service delivery process has stabilized; (2) this IT-enabled incremental customer service channel does not operate in isolation, but complements the existing channels. My findings suggest that when a firm integrates a self-service channel with a personal-service channel it releases employees from routine tasks so that they can focus on consultative tasks. Thus, both scholars and practitioners should consider the combined effect of the portfolio of the customer service delivery channels in order to ensure the optimal design of multi-channel IT-enabled customer service systems.