I called T-Mo and asked about unlocking the Vibrant to use foreign SIM cards, they said after 1 month they could unlock it. My question is, once it's unlocked can I travel to a foreign country and use a foreign SIM card (local to that country) on a 3G network on 2100Mhz, or would the phone revert back to 2G (850/900/1800/1900Mhz)? I ask because to use T-Mobile's 3G, it requires BOTH 1700Mhz and 2100Mhz signals.