1. A method of managing configuration of user equipment adapted for use in a cellular telecommunications network, the method comprising: receiving a user agent for installation on the user equipment; wherein the user equipment has (a) a processor, (b) an over the air (OTA) interface for receiving configuration data and a user agent, (c) a configuration data store for defining a configuration of the user equipment, and (d) a configuration manager for receiving configuration data in a compatible format which can be processed by the configuration manager for modifying the configuration data store; installing the user agent on the user equipment; receiving the configuration data to be used by the configuration manager for modifying the configuration data store, wherein the configuration data is in a format other than the compatible format, wherein the configuration data comprises an International Mobile Subscriber Identity Number transforming, using the installed user agent on the user equipment, the configuration data into the compatible format, and modifying, using the configuration manager on the user equipment, the configuration data store with the configuration data in the compatible format which can be processed by the configuration manager.