The concept of a locked phone or unlocked phone didn’t exist at first. When smartphones are produced, they’re all lock-free phones. You can choose and switch carrier without limitation. Locked phones mean that the internet and carrier are fixed for a period. It meets both clients and carriers requirements. On the one hand, people want to buy a phone at a price as cheap as possible.

On the other hand, Internet carriers limit the use of time and special terms of service to make a profit. After the mobile phones are recycled into the used mobile phone market, they will return to used phones unlocked.

The price of a locked phone is favorable, but the network is limited. It’s unfriendly for people who travel abroad or need to work abroad. In foreign countries or areas that are not supported by carriers, locked phones can only connect to the internet via WiFi.

At another time, with a smartphone that cannot be connected to the internet, life can become a difficult task. Therefore, buy locked or unlocked mobile phones is a worthwhile consideration. The people who use locked phones, when meets this situation, usually buy unlocked mobile phones to adapt. If you spend more money to buy a new phone, it is not worth it.

Generally, there are two ways of unlocking mobile phones according to the carrier’s official solution:
    1. You have to perform the purchase agreement signed with carrier until the contract is terminated.
    2. If you want to change the carrier when contract is not fulfilled, you can still apply for unlocking by paying liquidated damages.

Another way is by changing the activation policy of the IMEI. But such practices violate the rules of mobile phone manufacturers and internet carriers. Moreover, you cannot restore the system by self-unlocking. It is not recommended to do that. If you really need to change carrier without paying liquidated damages, a used phone unlocked is a viable option.