What is a NETWORK LOCK?

From EjWiki

SIM lock: A sim-lock, network-lock, carrier lock, imei-lock or (Master) subsidy lock is really a technical restriction built into CDMA and GSM mobile devices by producers to be used by service providers to limit using these phones to specific countries and/or networks. This is in comparison with a cell phone (retrospectively called SIM-free or unlocked) that does not impose any SIM restrictions.

Unlocking Technology: A device can be unlocked simply by entering a code supplied by the network operator. Different mechanisms consist of software working on the handset or a pc connected to the phone, hardware devices that link to the handset or over-the-air by the provider. In most cases the unlock procedure is permanent. The code required to remove all locks from a phone is referred to as the master code, network code key, or multi-lock code. Generally if the handset is carrier locked it will typically display one of the following messages: SIM network PIN blocked, Enter lock PIN.

Economics: The primary reason to unlock a mobile phone handset is to be able to utilize it with a different SIM card. Users may wish to carry on using their smartphone but with a new service or while traveling in foreign countries they might like to connect to a foreign network by using a pre-paid subscription.

Unlocking Services: Some organizations offer a permanent unlocking service. This service calls for all those who would like to unlock a device to provide their IMEI number to a service supplier and frequently they will also ask for the country and network the mobile is locked to, either sent by email or entered on their web-site. The supplier then will supply (at a cost to you) an unlock code for the handset.

Unlocking Service Providers: Unfortunately there are lots of scammers on-line retailers active in the smartphone carrier unlocking industry. Consequently it pays off to ensure you find a reputable service provider for these services. To aid with the search for a legitimate company, we have supplied a checklist below (and in no specific order) of several legit organizations currently offering such services.

Reputable Mobile Phone IMEI Unlocking Service Providers: Unlock BaseUnlock RiverCell UnlockerMobile UnlockedDoctorSIMUnlock.Zone