What is a Carrier Lock?
From EjWiki
SIM lock: A SIM lock, network-lock, Carrier-Lock, IMEI-Lock or (Master) SUBSIDY lock is actually a technical constraint built into GSM and CDMA phones by producers for use by providers to limit the usage of these phones to a particular locations and/or networks. This is in contrast to a phone (retrospectively called SIM-free or unlocked) which doesn't enforce any SIM constraints.SIM locking is incredibly common if subsidized handsets are offered with prepay contracts. It is crucial to note, however, that this technology linked with the cell phone will need to be compatible with the system being used by the network carrier. A GSM phone can only work with a GSM carrier and won't operate on a CDMA service. Moreover, a CDMA mobile phone will only work with a CDMA network and isn't going to work on a GSM network. Note that modern (2013 and newer) high end cellphones are equipped to support both CDMA and GSM technologies, letting customers to use their smart phones on any kind of network.
Unlocking Technology: A device can be unlocked by entering a code supplied by the network operator. Different mechanisms include software running on the device or a computer or laptop connected to the handset, hardware devices that connect to the handset or over-the-air by the carrier. Generally the unlock operation is permanent. The code needed to do away with all locks from a mobile phone is referred to as the master code, network code key, or multi-lock code. Generally if the phone is network locked it will typically display one of the following messages: SIM network PIN blocked, Enter lock PIN.
Economics: Mobile phone makers have monetary incentives both to enhance SIM lock protection (which placates network organisations and permits exclusivity discounts) and to weaken it (expanding a mobile's allure to customers that typically are not interested in the provider that offers it). In addition, making it too hard to unlock a phone may make it significantly less attractive to network service providers who have a legal obligation to offer unlock codes for certain handsets or in particular countries.
Unlocking Services: Lots of companies provide a unlocking service. This service calls for people who need to unlock a mobile phone handset to supply their IMEI number to a unlocking company and sometimes they will also require the country and cellular network the device is locked to, frequently sent by email or entered on their web-site. The company will then supply (for a fee) the unlock code for the device.
Unlocking Service Providers: Regrettably there are a lot of dodgy online retailers working in the smartphone unlocking industry. As a result it pays to ensure you find a reputable provider for this service. To assist with your search for a reputable service provider, we've provided a listing below (and in no specific order) of a few legitimate organizations currently offering such services.
Reputable Mobile Phone IMEI Unlocking Service Providers: Mobile UnlockedDoctorSIMUnlock.ZoneUnlock BaseUnlock RiverCell Unlocker
