Privacy constitutes a great challenge for the spread of new services. In particular for Next Generation Network (NGN) services, operators and providers hold more sensitive information than traditional networks. NGN implies a new service layer, accessible by third parties through standardized interfaces. This newly proposed service architecture is not protected yet against privacy threat. We demonstrate that pseudonymity is an interesting and feasible solution in Parlay X gateway.Location-Based Services (LBS) make use of user positions, which are sensitive information, to provide more enhanced services. Different alternatives in cellular networks, exist to retrieve this information, they however don't offer the same privacy quality level. Those alternatives may cooperate to provide location information to service providers. The discontinuity of the privacy quality imperils the anonymity of users. In this paper, we propose a novel Privacy web service added to the Parlay X gateway of the service architecture to ensure user privacy through pseudonymity in location services. The architecture is based on the enhancement of standardized Parlay X web services. The new proposed web service could enforce the privacy provided by operator networks. A formal model of our approach is investigated.