I am not sure if Arduino GSM Shield is compatible with the technologies of our local service providers , like AT&T or T-mobile, as it does not use EDGE or UMTS technologies to send data. The link for the list of cell phone service providers technologies is List of United States wireless communicat…

compatibility issues with AT&T or T-mobile sim card

system October 31, 2013, 8:07am 2

Arduino GSM Shield is compatible only with GSM operators. Not CDMA, UMTS and other types.

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