What is a IMEI LOCK?
From EjWiki
SIM lock: A SIMLOCK, network-lock, carrier lock, imei-lock or (master) SUBSIDY lock is a technical limitation built into CDMA and GSM mobile devices by producers for use by service providers to restrict the use of these phones to specific locations and/or networks. This is in comparison with a cell phone (retrospectively called SIM-free or unlocked) that doesn't impose any SIM constraints.
Most cell phones can be unlocked to work with any GSM network provider, though the phone may still show the original branding and may not support features of the new carrier. Aside from the locking, mobile phones may also have firmware placed on them which is specific to the mobile phone network provider. This firmware is installed by the service provider and is separate from the locking mechanism. The majority smartphones can be unbranded by re-flashing a different firmware variation, an operation recommended for advanced users only.
Unlocking Technology: Frequently, a locked mobile phone will show a message if a restricted SIM is used, requesting the unlock code. On modern phone models working on Android software, the cell phone should display a message stating “SIM network unlock PIN” or “Enter Network Lock Control Key” if it is network locked. Windows phones should display the message, “This SIM card can only be used on specific networks. Contact your customer service center for the unlock code”. Alternative models could display alternative messages for example "Enter special code" or "Enter unlocking code," or in some circumstances the handset will simply display a message stating that it's locked. The minute a valid code is entered, the handset will display "Network unlocked” or “Network unlock successful”.
Economics: Smartphone companies have economic incentives both to strengthen SIM lock protection (which placates mobile phone network companies and permits exclusivity deals) as well as to weaken it (expanding a smartphone's allure to buyers that may not be interested in the provider that offers it). Additionally, making it very hard to unlock a mobile might make it considerably less desirable to mobile phone network service providers who have a legal duty to supply unlock codes for certain devices or in specific countries.
Unlocking Services: Various companies offer a network unlocking service. This service needs individuals who wish to unlock a handset to provide their IMEI number to a unlocking company and frequently they will also ask for the country and service provider the handset is locked to, often sent via email or submitted on their web site. The company then will provide (at a cost to you) the unlock code for the phone. For some manufacturers as in Nokia and Samsung various services also supply special remote-unlocking software with instructions, when a cable connection is needed to remove the SIM lock from home. Such organizations may email the unlocking code or software that should remotely unlock the device. The cost for unlocking a cellphone may differ depending on the network it's locked to and the phone model itself, as every unlock code is unique to each individual device.
Unlocking Service Providers: Disappointingly there are a great deal of dodgy "businesses" working in the smartphone network unlocking industry. As a result it pays to ensure you locate a trustworthy service provider for these services. To aid with a search for a reputable company, we have supplied an inventory below (and in no specific order) of a few legit organizations currently offering such services.
