Abstract: Methods, apparatus and computer programs for changing a communication device from communicating with a first data communication system to a second system are provided. A change in the device's capabilities from a first to a second set is determined. A first message is sent to one system comprising one of the sets, and a second message is sent to a different system and/or comprising a different set, relative to the first message. The first message may comprise a detach request to the first system; the second message may comprise an attach request to the second system. The first and/or second messages may comprise an update request. Methods may comprise sending an update request, receiving a rejection, and sending the first message if the cause is among a predetermined group. One set may include radio technologies (e.g., LTE) not in the other set. Embodiments include apparatus and computer programs and computer-readable media embodying one or more of the methods.