you can't just switch a sim card and expect it to work instantly. But, has redsoxrocker has already pointed out, you'll need to unlock the device first. You can read up on how to do that.
You cannot unlock a cdma phone. With US Cellular there is no sim card slot on any phone from them. You put your sim card in the mini sd slot? That phone will only work on the US Cell network.
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Cdma phones search for specific towers that are pre programmed in the phone. It is a stupid feature(if you can call it a feature). I have tried in the past to get another carrier's phone activated on US Cell's network. You can get it going, but it will never find the towers you want.
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