If you need to find out your iPhone's carrier without a SIM card installed, you can do so through the Settings app.

To unlock your iPhone from its carrier, you'll likely need to contact your carrier directly to cancel your contract.

Have you ever gotten a new phone only to find out it’s locked to a specific carrier? This often happens when you purchase a subsidized phone from a carrier. The carrier locks the phone so you can’t ...

A user has an iPhone 3G from a relative in France. Has the phone, but no SIM card. Can't activate it initially because he has T-Mobile, so no valid SIM at all. I can't even use an ATT SIM (in US) so ...