Web Service (WS) composition has become a key element for the development of Service Orient Architecture (SOA) in the Next Generation Network/Next Generation Service (NGN/NGS) Context. From the viewpoint of user centric paradigm, existing work has limitation on whether the service composition satisfies the user requirements and has a context adaptation feature. This article presents our approach for solving these problems. Our proposal consists in a two level user centric approach for dynamic service composition, it is based on a composition engine which follows user's specific needs and which yields a composed service through a WS knowledge base. Users can mash up the services at run time with their own logic and have a fully dynamic composition with context adaptation through Virtual WS, the latter allows also semantic web.