Here's how the Apple SIM is supposed to work:
The new Apple SIM is preinstalled on iPad Air 2 with Wi-Fi + Cellular models. The Apple SIM gives you the flexibility to choose from a variety of short-term plans from select carriers in the U.S. and UK right on your iPad. So whenever you need it, you can choose the plan that works best for you — with no long-term commitments. And when you travel, you may also be able to choose a data plan from a local carrier for the duration of your trip.
Unfortunately, AT&T isn't supporting the interchangeability of this SIM card. If you try to activate an AT&T data plan you are presented with the following message:
"Once activation completes, this Apple SIM can only be used with "AT&T". You will need a new Apple SIM if you change carriers in the future."
T-Mobile and Sprint appear to be the only U.S. carriers to leave the SIM unlocked. Verizon isn't supporting it at all.
Apple acknowledges that some carriers may lock the SIM and says you can purchase another if need be from the Apple Store.
If your Apple SIM becomes dedicated to a specific network and you want to choose from other carrier programs, you can purchase a new Apple SIM from an Apple Retail store.
Read More [via MacRumors]