That's incorrect. You can power down the S3, put a AT&T sim card in, boot it up, and you have talk and text. The apnconfig must be modified to get data and MMS. Verizon 4g phones use a sim card because their 4G is technically a GSM frequency. Their 4G phones work natively for international carriers. Some of them work the same for US carriers, though most of them are blocked one way or another. The S3 is not.