Verizon won't let you switch it. I don't believe the 8330 has GSM capabilities.
Someone correct me if I am wrong but I don't even think that the 8330 has a sim card slot.
Even so, I don't think you will get great service using att on your Curve even if you can switch it over. It just doesn't have the GSM strength. Now the Tour or the Storm would be a different story but the radio could be shoddy even using those devices at times.
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