There are two major carriers that use SIM cards in the USA. T-Mobile and Cingular. You should make sure your cell phone is unlocked (which probably it is) and make sure you have the bands for the USA. If it is a quad-band phone you should be OK with either. If it is only a dual band or single band, you may be able to sign up only with one of the providers, depending which bands you have.
Can people who already have a cell phone merely get a new SIM card from a service provider? I'm living overseas and in a few months I move back to the US. The rest of the world uses this SIM card system, where suscribing to a service grants a little card, and buying a cell phone is seperate. I really like this phone, I spent a lot of money on it, and if possible I want to keep it in the US. Would a common provider like T-Mobile or Cellular Wireless grant me a SIM card? I haven't been ably to find any information on this.

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