An enterprise mobile network (2200, 2700) for providing wireless service within a coverage area associated with an enterprise using licensed radio frequency spectrum, the enterprise mobile network comprising: a base station subsystem (2208, 2706) deployed on a premises of the enterprise to provide wireless capacity within the coverage area using the licensed radio frequency spectrum; a mobile switching subsystem (2212, 2710) communicatively coupled to the base station subsystem using an Internet Protocol network, wherein the mobile switching subsystem is also communicatively coupled to a public land mobile network; and an Internet Protocol private branch exchange (2228, 2714) that is communicatively coupled to the mobile switching subsystem using the Internet Protocol network; wherein the enterprise mobile network is configured to have local subscribers thereof; and wherein at least one local subscriber has assigned thereto a local mobile phone number and a private branch exchange extension number; the mobile switching subsystem comprising a Session Initiation Protocol user agent configured to register the local mobile phone number with the Internet Protocol private branch exchange and appear to the Internet Protocol private branch exchange as a Session Initiation Protocol phone when said local subscriber is camped on to the enterprise mobile network; wherein for said at least one local subscriber, when an attempt by a calling party to set-up a call made to that local subscriber's private branch exchange extension number is received at the Internet Protocol private branch exchange, the Internet Protocol private branch exchange is arranged to interactwith the Session Initiation Protocol user agent in the mobile switching subsystem as if the Session Initiation Protocol phone in order to cause a mobile device associated with that local subscriber's local mobile phone number to indicate that an incoming call is being made, wherein if that local subscriber answers the call using the mobile device associated with that local subscriber's local mobile phone number, the call is set up between the calling party and the mobile device associated with that local subscriber's local mobile phone number using the Session Initiation Protocol user agent in the mobile switching subsystem; and the Internet Protocol private branch exchange is arranged to cause a device associated with that local subscriber's private branch exchange extension number to indicate that an incoming call is being made, wherein if that local subscriber answers the call using the device associated with that local subscriber's private branch exchange extension number, the call is set up between the calling party and the device associated with that local subscriber's private branch exchange extension number. a base station subsystem (2208, 2706) deployed on a premises of the enterprise to provide wireless capacity within the coverage area using the licensed radio frequency spectrum; a mobile switching subsystem (2212, 2710) communicatively coupled to the base station subsystem using an Internet Protocol network, wherein the mobile switching subsystem is also communicatively coupled to a public land mobile network; and an Internet Protocol private branch exchange (2228, 2714) that is communicatively coupled to the mobile switching subsystem using the Internet Protocol network; wherein the enterprise mobile network is configured to have local subscribers thereof; and wherein at least one local subscriber has assigned thereto a local mobile phone number and a private branch exchange extension number; the mobile switching subsystem comprising a Session Initiation Protocol user agent configured to register the local mobile phone number with the Internet Protocol private branch exchange and appear to the Internet Protocol private branch exchange as a Session Initiation Protocol phone when said local subscriber is camped on to the enterprise mobile network; wherein for said at least one local subscriber, when an attempt by a calling party to set-up a call made to that local subscriber's private branch exchange extension number is received at the Internet Protocol private branch exchange, the Internet Protocol private branch exchange is arranged to interactwith the Session Initiation Protocol user agent in the mobile switching subsystem as if the Session Initiation Protocol phone in order to cause a mobile device associated with that local subscriber's local mobile phone number to indicate that an incoming call is being made, wherein if that local subscriber answers the call using the mobile device associated with that local subscriber's local mobile phone number, the call is set up between the calling party and the mobile device associated with that local subscriber's local mobile phone number using the Session Initiation Protocol user agent in the mobile switching subsystem; and the Internet Protocol private branch exchange is arranged to cause a device associated with that local subscriber's private branch exchange extension number to indicate that an incoming call is being made, wherein if that local subscriber answers the call using the device associated with that local subscriber's private branch exchange extension number, the call is set up between the calling party and the device associated with that local subscriber's private branch exchange extension number.