Currently, it is legal in all countries to unlock cell phones and use any SIM card in any GSM phone. As previously stated, most carriers will not advertise this service though because they want to sell you a phone, or keep you in a contract. If a person is obligated to a contract they can stay with the carrier, but find an unlocked phone that is more desirable or suitable for their needs. Unlocked cell phones are also very convenient when a contract is still in tact, but the originally purchased phone has been lost, damaged, or stolen.

Unlocked cell phones work with GSM enabled phones only; therefore, any carrier that services GSM phones will support unlocked cell phones. However, most carriers do not advertise unlocking services, which leaving customers unaware of the concept and benefits of unlocking phones and switching SIM cards. Furthermore, customers are often scared away by the high price of unlocked cell phones without understanding the long-term savings of unlocked devices.

International travelers often find unlocked cell phones to be a cost -effective alternative to paying international calling fees. Any GSM cell phone can be unlocked and a customer can insert a pre-paid SIM card to pay for international calling. This can add up to substantial savings, depending on how many calls are made and the price of the pre-paid plan.

To find a carrier that supports unlocked cell phones simply find out if they sell GSM cell phones. GSM phones are the only type of cell phones that use SIM cards, which is what is needed to be able to switch between unlocked devices. If you purchase an unlocked phone, but it is without a SIM card, ask the carrier of your choice if they can give one to you. The SIM card should be free, as this is what will provide the phone service you will be paying for anyway.

Keep in mind that if a person decides to switch SIM cards between phones, each phone needs to be unlocked for this to work. Some carriers will provide a code which will unlock a cell phone. Customers can also choose to pay a private company, either in person or via Internet, to help unlock a cell phone. Another option is to purchase the phone already unlocked, however buyers should be careful when purchasing from online retailers as some phones are not truly unlocked. Here we are highly recommeder a online shop China Yotang which sell unlocked cell phones for several years!

Generally speaking, the U.S. carriers that sell GSM phones and that operate by way of SIM cards include AT&T, T-Mobile, Boost Mobile, and Nextel. Pre-paid SIM cards can be found around the world. In Australia, JUST Prepaid Mobile as well as Passport SIM Card can be purchased to offset the high cost of international calls for travelers.

some other opinions:
1.Unlocked GSM world phones will often support international WCDMA networks. This allows you to use these phones with carriers in Japan and South Korea, places where world phones were once incompatible.

Another reason it is easy to buy an unlocked phone is that almost every country that has cellular telecommunications supports GSM. This creates a huge market for unlocked world phones. If you look at most of the phones in the showrooms of GSM carriers, you can find the exact same phone in an international version. This is essentially the unlocked version of the phone. The only downside of buying international phones is they do not honor the warranty in the United States. This is the last bit of control that American cellular telecommunications has over the ability to lock a specific phone to a carrier.

2  I didn’t think that CDMA networks like Verizon and Sprint supported unlocked cell phones. They will unlock their world phones to be used on global GSM networks, but you cannot buy a CDMA unlocked cell phone to use on a CDMA network. I do not think that you can transfer a Sprint phone to Verizon’s network either.

I love being able to have an unlocked phone, and for this reason I will not sign a contract with a CDMA carrier. CDMA carriers also tend to be a little more expensive because CDMA technology is a little more advanced.