A cellular data communication interfacing apparatus, for association with a mobile network and for supporting cellular data communication to roaming mobile telephony devices, comprises a data request analyzer, a service network selector, and an interfacing engine. Each of the roaming telephony devices is associated with a respective home network and a service profile specifying service networks providing data services to the device. The data request analyzer analyzes data requests from the roaming mobile. The service network selector uses the request analyses together with the device service profiles to select a corresponding service network. The interfacing engine introduces the devices to the service networks, directs the data requests to the service networks, and directs the corresponding data responses from the service networks to the requesting roaming mobile devices.