1. A system for provisioning call models within an IP Multimedia Subsystem (IMS) network so that different users can have distinct IMS service experiences, said IMS network including a serving call state control function (S-CSCF) for providing session control for user endpoint (UE) devices, said system comprising: a database of call model information, said call model information being selectable based on at least one of a user identity and a group identity, said database associating service requests with application servers (ASs), said association based on at least one of a user identity and a group identity; S-CSCF logic to receive a service request having a user identity or group identity and to access said database of call model information with said user identity or group identity; mobile environment (ME) server logic to use the database of call models and network topologies to construct a new set of filter codes and store the new set of filter codes in a Home Subscriber Server (HSS) database for the user identity or group identity; and S-CSCF logic to instantiate a call model using the new filter codes in response to receiving said call model information, the new filter codes having service point triggers (SPTs) identifying the corresponding AS having service logic to provide a service for the service request, wherein at least two call models have different new filter codes, SPTs, and ASs with different service logic, such that the two call models provide distinct service experience for said service request, and wherein constructing the new filter codes permit dynamic changing of the association between a user identity and the service logic based on network topologies.