People don't seem to realize that cellular phones are incredibly different from regular phones. A cellular phone is actually a radio transmitter and receiver. When talking on a cellular phone, or even when using a normal phone and talking to somone on a cellular phone, the conversation is being broadcast, and can be easily intercepted. Cellular phones do NOT provide privacy. The average cellular phone is capable of doing a lot more than just being set up for service and used the way the cellular providers intend them to be.
Most cellphones have a test mode, where special functions can be accessed.
More interesting functions include being able to use the cellphone as a scanner, scrolling through the cellular frequencies eavesdropping on other people's radio broadcasts. Things get even more interesting for the hacker when he discovers how easy it can be to clone a cellphone. This allows cellular fraud to happen. This text is only to show how easy it is to commit fraud on the cellular network, and is not intended to encourage people to use the information for personal gain. This information is broadcast from the phone and picked up by the cell tower.