This case study seeks to increase understanding of how agency is fostered in human-AI interaction by providing insight from Uber’s development of a conversational voice-user-interface (VUI) for its driver application. Additionally, it provides user researchers with insight on how to identify agency’s importance early in the product development process and communicate it effectively to product stakeholders. First, the case reviews the literature to provide a firm theoretical basis of agency. It then describes the implementation of a novel in-car Wizard-Of-Oz study and its usefulness in identifying agency as a critical mediator of driver interaction with the VUI before software-development. Afterward, three factors which impacted driver agency and product usage are discussed – conversational agency, use of the VUI in social contexts and perception of the VUI persona. Finally, the case describes strategies used to convince the engineering and product teams to prioritize features to increase agency. As a result, the findings led to substantive changes to the VUI to increase agency and enhance the user experience.