As of 2015, the iPhone 5 is available without a data plan contract. A phone that is not assigned to a carrier contract is called an unlocked phone. An iPhone 5 can be purchased unlocked or, in some cases, can be unlocked by a carrier.
If a carrier unlocks an iPhone 5, the customer is then able to use the same phone with another carrier. After unlocking an iPhone 5, the SIM card can be removed and replaced with the new carrier’s SIM card. In some cases an error might appear after installing the new SIM card. Restoring the unlocked iPhone to factory settings is then recommended to correct the issue.