Chat services that provide real-time help for customers have been adopted widely and rapidly on many websites in the past few years. Our paper investigates online live chat customer services from two perspectives: media choice between chat service and web e-mail, and media use of chat service analyzed from the perspectives of characteristics, interactivity and socioemotional content. We collected four types of data including system log files, surveys, excerpts of chat transcripts, and unstructured interviews with service representatives. In addition to quantitative data analysis, ATLAS.ti was used to analyze qualitative data in our study. We found that for the purpose of seeking help with questions, more users chose to use web email than chat service. When using the chat service, representatives and users interact with each other through text exchange, page pushing, and co-browsing. They also perform activities such as clarification and attracting attention, and use socioemotional content such as greetings and expressing feelings.