Your SIM card will be linked to your account and any data you use will be added to your bill. You can’t buy a data-only SIM instead of a voice and data SIM. It’s an add-on, not a replacement.

Remove the SIM card and store securely. An easy way to make sure you can switch out SIM cards quickly—as soon as you land stateside, for example—is to carry a paperclip on your keychain or ...