An aspect of the disclosure provides a method of admitting a session from a user device subscribed to a service with a virtual network operator. The method includes receiving a service request from said user device at an Access Point and selecting a network function Authentication and Authorization (AA) function (AAF) to confirm the user device is authorized for the requested service, and transmitting the request to the selected network function AAA function. The AAAF which processes the request may reside with the virtual network operator (VNO). However, the VNO may share its AAA database with other network entities (for example, Telecom Connectivity Service Providers (TCSPs) or InPs), and allow those entities to perform the AAA functions.