The invention provides an apparatus and method of associating communication service sessions with geographical locations. Each of a multiplicity of user devices, attached to one or more access networks via respective access points, can determine the identity of an access point serving that particular user device. The user device then registers with a location service, via the access network, both the network access point identity and a geographical address at which the access point is located. The location service can then use the registered access point identity and geographical address to register the user device, or another user device, in a communication service in association with said geographical address. In this way, the geographical address of a registered user device, which is associated with a particular communication service session, can be determine.