Sim Cards....how do they work?

Does the Sim Card already come in your phone when you buy it ? Or can you buy your own Sim Card and put it into any phone? I don't really understand how the whole thing works.Thanks

Sim Cards....how do they work?
well it depends on what phone u have do u have cingular t Mobil dos Ur phone even have a Sims card i have a Pre paid phone every Time i get a new one i just put in my old sims chip and it works i have had three phones that iv did it to and u can buy ur own but u have to get it activated on line or bye who ever ur Carrier is
Reply:Cingular phones use a SIM card...that card identifies your account. It stores your phone #'s, downloads, etc...


You can buy one in a store that carries SIM phones...When you buy a new phone, you can put your SIM in it....but usually does come with a new one. The newer ones can hold more info....to transfer your address book from one to another, the store can put them on a SIM reader. Downloads are not transferable.


If you do get a new SIM card, you must call CS to activate it.