International cell phone service varies greatly from the service that Americans' receive here in the United States. In fact, the difference in the service is go great on so many levels that cellular phones that are made for usage in the United States will not work overseas. The two major differences that exist between the mobile phone systems abroad and here at home involve the frequencies and the type of networks that the systems operate on.
As mentioned above, the two major obstacles to being able to have international cell phone service are the differences in the frequency and network setup used. Many countries overseas use the same network, known as the GSM network, which is different from the network that cellular phones in the United States use. Therefore, while an international phone will work in multiple countries overseas (over 200), it will not work in the United States. However, many companies in the United States are beginning to switch over to the GSM network. The bad news however, is that they still operate at a different frequency, meaning that they are still inoperable on the international network.
This leads to the second difficulty in optaining international cell phone service, the difference in frequencies used. Phones that work on the international GSM network operate on one of two frequencies, 900 Hertz (Hz) or 1800 Hz. Phone companies in the United States, however, program their phones at 1900 Hz, a frequency level that is in no way compatible with either international level. There are some countries that are an expection to the frequency rule however. For example, Canada, Mexico, Japan, Korea, and some Central and South American countries all use frequencies other than the two given international ones.
Some United States phone companies are attempting to come up with a solution to this international cell phone service problem. They are proposing multiband phones that can switch back and forth between frequencies. The most common multiband phones at the moment are ones that switch back and forth between two or three different frequencies so as to cover most or all of the 900/1800/1900 Hz. frequencies that are used globally.