1. A Proxy Call Session Control Function (P-CSCF) server for enabling multiple users to access, through one or more types of IP connectivity access network (IP-CAN), an IP Multimedia Subsystem (IMS) offering multimedia services to the users, wherein the P-CSCF server is configured to perform the following for each user and access type: receive a registration request from a user having a signaling session established through an IP-CAN with the P-CSCF server, the registration request requesting to access the IMS; send to a Policy Control Rules server, a configuration request for P-CSCF configuration data to configure the P-CSCF server, said configuration request including information identifying the user; receive from the Policy Control Rules server, the P-CSCF configuration data, the P-CSCF configuration data being dynamically selected by the Policy Control Rules server and including: one or more instructions to modify or reject service information in transit between the user and the IMS based on access-related user information; and information about an access type of the IP-CAN through which the user has established the signaling session with the P-CSCF server; configure the P-CSCF server in accordance with the dynamically selected P-CSCF configuration data; and modify or reject service information in transit between the user and the IMS based on the received information about the access type of the IP-CAN.