The only options for the iPhone 4 that's not running baseband 01.59.00 is either a hardware unlock using an interposer or a factory/IMEI unlock. Prices are about the same, but, the interposers like the Gevey that Justin recommended, does not support all iOS and baseband models in the future as far as we know. The IMEI/factory unlock will support every iOS and every baseband that will ever be created until the iPhone 4 gets to the point that the original iPhone is now, unrecognized, obsolete and replaced with a superior iPhone generation.