If I had to choose one of the most annoying features cell phones it would be SIM Lock. SIM lock is a feature implemented by mobile phone manufacturers / providers to allow only the use of SIM cards in the phone that meet specific criteria. Currently, phones can be locked to only accept SIM cards from one or more of the following:
- Providers (most common)
- SIM types
In plain English? SIM lock is the feature that can:
- prevent you from running your cell phone under different SIM card (this is also why you usually receive a new SIM card every time you buy a new phone), or
- prevent cell phone usage of phone abroad, or
- prevent you from using some of the available services, and
- is one of the main culprits for “Insert correct SIM card” errors
Sound like a feature every consumer wanted and needed for their cell phone ;)
The bottom reason SIM locks exist is commercial - it makes possible for service providers to provide cheap pay-as-you-go handsets. Is this a good deal for the user? My personal take is a definite no.
The fun starts of course when you need to unlock a locked phone. Unlocking the phone is not hard - in theory.
All you need is to enter a special code (also known as master code or network code key) by typing the code manually or receiving it over-the-air by the carrier. The bad news? In order to get this code you need to visit an authorized service provider reseller or request unlocking from service provider customer support (in both cases: be prepared for longish wait).
To make things worse: in some cases unlocking is made totally impossible - for example service provider might disallow unlocking based on terms of service. The third, less talked option is breaking / hacking the SIM lock. This is in most countries about as illegal as it sounds and works mainly with Nokia branded phones.