Do AT&T cell phones work with other companys that use sim cards as well?
The only other company that AT&T cell phones would work with is T-Mobile. They have SIM card and also work on the same frequency as AT&T does. However you can also unlock the phone and take them to Europe where they will work, but other carriers such as NexTel or Sprint (That do use sim cards also) wont work because of the Technology ... example GSM or 3G that are not compatible with that carriers Technology since they use CDMA.
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