I recently moved from the UK to the US and cancelled my UK mobile contract. The contract got shut off the other day, with the iPhone saying "No Service" in the status bar and basically being a glorified iPod Touch. As far as I understand (but correct me if I'm wrong), when activating iMessage the phone sends a hidden text or data message to the carrier and receives one back (all hidden from view) to confirm the phone number. I'd imagine that after initial activation it does this periodically just to confirm the number is still the same (I know that in the US deactivated numbers get back in circulation relatively quickly, so Apple and the carriers have to somehow make sure that you don't get the messages of the new owner of the number, in the UK it takes quite a while for a number to go back on the pile of usable ones). I won't be able to get a new T-Mo US sim for at least a week or two, so I'd like to still be able to use iMessage on my old number. At the moment this still works without problems. How long will I be able to keep iMessage working on my old number before it checks the number with the carrier and realizes it doesn't exist anymore? TL;DR: My number is no longer in use, how long can I keep using iMessage on it?