Pick a cell phone service provider
Wireless carriers in the United States operate over two different networks: Code Division Multiple Access (CDMA) and Global System for Mobile Communication (GSM). Though each technology transmits voice and data, they do so in different ways, which makes them incompatible. As a result, you can't take a CDMA phone and use it on GSM or vice versa.
Of the U.S. carriers, AT&T and T-Mobile use GSM, whereas Sprint, Verizon, and smaller carriers such as MetroPCS and U.S. Cellular use CDMA. Many of these carriers offer prepaid services. Verizon, for example, has its own prepaid plan page.
CDMA coverage is very strong in the United States, particularly in rural areas, but GSM service has a larger global footprint (it's the standard in Europe, for example) and GSM phones use the convenient SIM cards, which allow you to, among other things, switch phones more easily. Also, when taken on a global scale, GSM users will find a wider selection of handsets. Note: SIM cards now come in a smaller micro-SIM design to accommodate thinner handsets. Not all phones support both sizes, so be sure to check and see which size cards the phone uses before swapping handsets.
With that in mind, if you travel overseas frequently or you enjoy switching out your phone often for the newest model available, then GSM is the better choice. Not all GSM phones will work overseas, however, so be sure to read CNET's guide to world phones. But if you'll be making calls mostly in the United States, then CDMA is an equally good option. What's more, some CDMA phones now also support GSM networks for international use.
The LG Optimus 4X HD is an unlocked GSM phone.
Besides technology, there are other factors that should play into your carrier decision. You should begin by deciding which carrier has the most economical service plans and the most attractive selection of phones. The quality of customer service is another determinant, but that can be difficult to evaluate beforehand. Since knowing the pros and cons of each operator isn't easy, we invite you to take a closer look at service providers in our guide to cell phone carriers.
Besides the major operators, you might also consider Mobile Virtual Network Operator (MVNO) carriers that cater to a special demographic or lifestyle. For example, Virgin Mobile is targeted toward younger users, whereas Boost Mobile is centered on urban users who want advanced features. MVNOs do not operate their own cellular network; they lease network space from national carriers.
Ultimately, though, you should base your decision on which carrier offers the best reception in your area. Because evaluating wireless coverage requires experience with the network in a wide variety of physical locations, CNET does not rate wireless carriers, but we've partnered with Root Wireless to create a tool for determining the best carrier for your neighborhood, commute, or workplace. Word of mouth also is helpful when selecting a provider.
Since reception varies sharply by location, ask your friends and family which carrier they use. Also, since there's no substitute for real-world experience, ask to borrow a friend's phone and test it in your house and your workplace. Remember that carriers have a grace period during which you can test the service and return the phone without voiding the contract. Yet if you do return a phone and cancel a contract, you may have to pay for calls made during the usage period.
