Back in the late 2000s and early 2010s, it was difficult to find an unlocked phone in the U.S. Most cellphone companies "locked up" their phones, to prevent you from switching over to another company easily. This meant that the on-board SIM card couldn't be switched to another service. Thankfully, those days are over.
Now, when you buy a smartphone directly from a cell service provider, whether at the store or as part of a contract plan, that phone is likely to be "locked" to the provider's particular network only for a set amount of time. After that period, most providers will allow the phone to be "unlocked" automatically. Then, you have the freedom to use the same phone with a different company, or switch phone numbers and service accounts.
In this article we'll explain the story behind locked and unlocked phones plus how to unlock your phone should it still be in "lock" mode.