The use of virtual agents to intelligently interface with online customers of e-commerce businesses is remarkably increasing. Most of these virtual agents are designed to assist online customers while searching for information related to a specific product or service, while few agents are intended for promoting and selling a product or a service. Within the later type, our aim is to provide proactive agents that recommend a specific item and justify this recommendation to a customer based on his purchases history and his needs. In this paper, we propose a dialectical argumentation approach that would allow virtual agents that have sales goals to trigger persuasions with e-commerce's customers. Then, we illustrate the proposed idea through its integration with an example from real-life.