He writes: "My iPhone came complete with SIM installed, and once I had downloaded and installed the latest version of iTunes, it took less than 20 minutes to activate the phone and it worked ...

Activating a new Sim card isn’t always as straight forward as it sounds. This handy guide will take you though the process for the biggest networks.

Multiple users have noted that once you activate the Apple SIM on AT&T's network, it can only be used on AT&T's network and you'll need a new Apple SIM if you want to change carriers in the future.

AT&T has confirmed in a statement that the new universal Apple SIM card in iPad Air 2 and iPad mini 3 becomes locked to the carrier after being activated on its network.