This study examines the role that chatbots, an application of AI in e-commerce customer service, play in increasing online trust in brands and how, from this trust, interaction with chatbots can impact brand preference and purchase intention A conceptual model based on the Technology Acceptance Model (TAM) and Information System Success Model (IS) is proposed to understand the relationships between the utility, ease-of-use, and responsiveness of a chatbot, online trust, brand preference, and purchase intention. Based on a sample of Spanish consumers, this study provides a better understanding of how to build trust online and how this can strengthen the relationship with the consumer and lead to a purchase. At the same time, it alerts professionals to the need to design chatbots that are useful and respond efficiently and quickly in their customer service. The results of our study aim to help brands in designing chatbots to provide e-services that consolidate customer relationships and foster sales.