When speaking of a “locked” cell phone on this web site, we mean a cell phone that is restricted to a particular service provider (network). This restriction prevents you from using your cell phone on a different yet compatible network. So it would be more correct to call this type of phone “network restricted”.

Let’s say you have a GSM or iDEN cell phone, when you insert a SIM card from a different network, you probably will see one of the following messages: Remove phone restriction, Enter Subsidy password, SP (Service Provider) lock, Phone restricted, NCK, NSCK, SPCK locked, Insert Correct SIM Card, Phone Restricted, Enter Special Code, Contact Service Provider, Cannot Undo Restriction, Wrong SIM Card, Not Allowed error, SIM locked, Subsidy locked.

This means you are restricted to use only the service / SIM card from that one particular network provider. If you want to use a SIM card or service or another provider, your phone will reject it.

This is true even if you have a world phone. You can’t really use other providers in other countries, which makes it either prohibitively expensive if your destination has roaming agreement with your home network, or useless if it doesn’t have roaming.

There are also different levels of locking to the network such as Service Provider (SP) lock, Network Lock, Network Subnet Lock, and Corporate Lock. The most common is SP/SIM lock. Note: this is different from the personal PIN or security code you set yourself to protect your phone from being used by unauthorized persons or the SIM PIN code you use to protect your phone book. In the latter case you have a SIM-protection or phone-protection, not a SP (service provider) or SIM or phone network restriction.

Common error messages you’ll find are: “Enter Subsidy Password”, “Enter Special Code” (Motorola), “Phone Restricted” (Nokia), “Insert Correct SIM Card” (Ericsson, Siemens), etc.

For example, if you have service with XYZ Wireless. You paid for your phone and yet it is locked to XYZ network. If you try to use ABC Wireless SIM card, your phone won’t accept it. If you take it abroad and try to use Orange SIM card, you won’t be able to either. Once your phone is unlocked (unrestricted), however, you will be able to use any SIM cards you like, whether it’s ATT, T-Mobile, Cingular, Orange, Vodafone, TIM, China Mobile, etc.

Why should I consider unlocking my phone?

If you are considering one of the following, you must unlock your phone first:

1. If you need to travel abroad and save a lot of money on phone bills

2. You want to switch wireless providers

3. You need to resell the phone

4. You bought a second-hand phone (most likely locked)

Most wireless carriers are likely to give you a run-around when you try to request an unlocking solution. Why waste your valuable time driving to the service center only to be told that they can’t unlock the phone for you. You will then make a twenty minute call and the customer service may or may not be willing to help you.

Can I use my phone for international travel?

If you have a GSM phone and it is a world phone, then the simple answer is yes. To find out whether your phone will work abroad or not, you must know the model and band it uses. Most North American countries use 1900MHz or 850MHz. All other countries use 900MHz and/or 1800MHz. If your phone does not have the band frequency required abroad, then you’ll need a world phone. Unlocking a non-world phone will not change the hardware radio frequency.

Does unlock mean that I could use a 1800/900MHz phone here in the US?

Unfortunately, in most cases, No. If the phone is not designed to support GSM network 1900MHz band, then you cannot use it even if it is unlocked. Unlocked phone means you are free to choose network provider but it does not mean you can change the hardware limitation of the phone. If you are planning to use your phone in the US, make