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

If you're an AT&T customer, you can unlock your phone using a portal on the AT&T website. You'll need to have paid all of your bills first.

ZDNET's key takeaways Use these codes to forward calls, pay your bill, check balances, etc.Some of the codes work only on certain carriers or devices.One of the codes also might erase your data, so ...