1. A mobile end-user device comprising: a modem to access a network data service through a mobile access network; a user interface; and a service processor configured to: request, through a secure Application Programming Interface (API) of a network element accessed via the mobile access network, a service selection set; obtain, in response to the request, a corresponding service selection set comprising service plan descriptive information and actionable user selection options; extract information from the service selection set; present a notification message containing information from the service selection set through the user interface; obtain, through the user interface, a user response to the notification message; generate a response message comprising information specifying a user choice from among the actionable user selection options in a format expected by a selection set user selection receiver; and send the response message to the secure API.