Europe is an entirely GSM continent, and your EVO's voice/text/data features will not work there, since it cannot connect to their network. Your WiFi will work just fine, and without a charge from sprint. You may want to turn off your mobile network, just to save on battery life since your phone might constantly search for a signal that it won't find. But you won't have to worry about coming back to the US with any roaming charges since the Evo will not connect to any towers
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