A system for sending a relay notification comprises a transceiver and a processor. The processor is configured to use the transceiver to receive a request for allowing a mobile device to be used by a further mobile device as a relay to a mobile communication network. The processor is further configured to determine whether the mobile device is to act as a relay for the further mobile device based on the unique identifier of the further mobile device, and to use the transceiver to notify the mobile device that it is to act as a relay for the further mobile device in dependence on the determination. The mobile device is configured to receive the notification from the system. The processor is further configured to start relaying data received from the further mobile device to the mobile communication network upon receiving the notification.