A system comprising: a communication device to receive incoming calls at an extension on a PBX network and to initiate a call session for each incoming call; and an application server to: render virtual PBX services at the extension, the virtual PBX services having one or more configuration parameters for configuring the call sessions, wherein one or more of the configuration parameters are pre-provisioned; present a user interface configured to receive a user command to access the one or more configuration parameters; receive an update to one or more of the configuration parameters through the user interface, wherein the update to the one or more configuration parameters includes an update to one or more call handling rules configured to handle the incoming calls to the extension; update the virtual PBX services based on the one or more updated configuration parameters; and render the updated virtual PBX services at the extension; the application server further configured to: display a first configuration menu for the extension, the first configuration menu comprising multiple user interface elements, an arrangement of the multiple user interface elements corresponding to a progression of a call to or from the extension; receive a user request to select one of the multiple user interface elements, the selected user interface element corresponding to a second configuration menu for the extension; characterised by: receive a user request to register a location for an enhanced emergency service E-911 service through the selected interface element and populate an address registration corresponding to the extension to effect an updated configuration parameter for the extension, the updated configuration parameter being associated with E-911 call handling rules configured to handle outgoing E-911 calls from the extension such that an E-911 call originating from the extension is automatically associated with the address registration associated with the extension. a communication device to receive incoming calls at an extension on a PBX network and to initiate a call session for each incoming call; and an application server to: render virtual PBX services at the extension, the virtual PBX services having one or more configuration parameters for configuring the call sessions, wherein one or more of the configuration parameters are pre-provisioned; present a user interface configured to receive a user command to access the one or more configuration parameters; receive an update to one or more of the configuration parameters through the user interface, wherein the update to the one or more configuration parameters includes an update to one or more call handling rules configured to handle the incoming calls to the extension; update the virtual PBX services based on the one or more updated configuration parameters; and render the updated virtual PBX services at the extension; the application server further configured to: display a first configuration menu for the extension, the first configuration menu comprising multiple user interface elements, an arrangement of the multiple user interface elements corresponding to a progression of a call to or from the extension; receive a user request to select one of the multiple user interface elements, the selected user interface element corresponding to a second configuration menu for the extension; render virtual PBX services at the extension, the virtual PBX services having one or more configuration parameters for configuring the call sessions, wherein one or more of the configuration parameters are pre-provisioned; present a user interface configured to receive a user command to access the one or more configuration parameters; receive an update to one or more of the configuration parameters through the user interface, wherein the update to the one or more configuration parameters includes an update to one or more call handling rules configured to handle the incoming calls to the extension; update the virtual PBX services based on the one or more updated configuration parameters; and render the updated virtual PBX services at the extension; the application server further configured to: display a first configuration menu for the extension, the first configuration menu comprising multiple user interface elements, an arrangement of the multiple user interface elements corresponding to a progression of a call to or from the extension; receive a user request to select one of the multiple user interface elements, the selected user interface element corresponding to a second configuration menu for the extension; display a first configuration menu for the extension, the first configuration menu comprising multiple user interface elements, an arrangement of the multiple user interface elements corresponding to a progression of a call to or from the extension; receive a user request to select one of the multiple user interface elements, the selected user interface element corresponding to a second configuration menu for the extension; characterised by: receive a user request to register a location for an enhanced emergency service E-911 service through the selected interface element and populate an address registration corresponding to the extension to effect an updated configuration parameter for the extension, the updated configuration parameter being associated with E-911 call handling rules configured to handle outgoing E-911 calls from the extension such that an E-911 call originating from the extension is automatically associated with the address registration associated with the extension.