Most cell phones in the world (with the exception of the United States) are built to use a Subscriber Identification Module or SIM card. The SIM card is a tiny chip that carries all the information about the phone and its users. SIM cards ease the transition from an old phone to a new one by having all your old phone's number, phone directory, recent text messages, and tons of information transferred by simply plugging it into the new cell phone. Currently, SIM cards are designed to be only used with the cell phone carrier that issued it. When talking about unlocked cell phones, a locked cell phone is a phone that artificially prevents SIM cards from other carriers from working with the phone. For example, a locked T-Mobile phone cannot be used with a AT&T SIM card. If an unlocked cell phone is used, however, any SIM card can be used with it without having problems. Having a phone unlocked can be as simple as changing some software settings.

Unlocked mobile phones have been a very popular idea in the United States much to the dismay of cell phone carriers. Many carriers in the United States don't like the idea of having phones unlocked due to the fact that they're giving their phones out for nearly free with their contracts. If people jumped out of their contract after receiving their $500 phone for less than $50, the carriers could stand to lose a lot of money. Thus, they lock the phones to prevent people from doing that. While it makes good business sense to do that, many consumers feel cheated or abused by that concept. Fortunately, many carriers have recently looked into allowing people to unlock their phones after a certain period of time has passed. T-Mobile, for example, will let you unlock your phone after 90 days of service.

Be that as it may, many consumers and consumer rights groups feel cell phone carriers are out of bounds with their policies. There have been a few class action law suits filed to have those polices changed by those groups. While many carriers policies have been changing, many consumers still feel that "little change" is not enough. The idea behind the lawsuits is carriers should change the software behind locked cell phones to make it easier to unlock. Some phones have hidden proprietary codes that can potentially damage or render the phone unusable if handled wrong. So, unless the cell phone carriers change their policies towards locked cell phones, many consumers will go out and buy factory "unlocked" mobile phones or even try to unlock their phones themselves.

If you want to buy an unlocked cellular phone, you can either get one from a website like eBay or exclusive cell phone sales sites, or from a local business specializing in unlocked phones. When buying an unlocked phone, make sure you buy one that is factory sealed and is completely new. Buying a pre-owned phone can result in problems especially if the used phone was stolen (unlocked cell phone scams are common). Some people don't like buying "new unlocked phones" because of their large cost. Some unlocked phones can cost hundreds of dollars which is unaffordable for many cell phone buyers. So, a secondary choice to buying an unlocked phone is using a service to unlock the phone for you. Many websites offer software that will help you unlock your phone. There are also many local businesses and people that will unlock your phone for a fee. While these secondary methods for unlocking a phone are much more affordable, they can also have a lot of problems. If, for example, the wrong steps are taken when unlocking your phone, you can end up with a broken phone that can't make or take calls at all. So, for best results when dealing with unlocked phones is to buy a new phone.