Carriers also won't unlock a phone if it has been ... carriers "piggyback" on larger networks. AT&T phones are compatible with Consumer Cellular, for example.) Buying a used phone?

In some cases, phones currently need to be unlocked manually through a customer request. Manually needing to ask cellular carriers ... making a difference at the consumer level.

That's where unlocking comes in. When you unlock your phone, you get full ownership of the device. This means that you can then switch cell phone carriers without having to buy a new device.