Even though T-Mobile "Unlocked" my Samsung Galaxy S2 and i pay the tethering charge in the US (which works fine), when i go to other countries and use their SIM cards, i cannot tether. When i try i get an error that says "...Invalid SIM" In all three countries: Australia (Telstra and Vodaphone), England (3) and the Bahamas (BTC) the phone calls, access to the internet at 3g and 4G speeds, emails and texts all work just fine. But when i try to tether, the blue icon for tethering flashes quickly and then gives and error "...Invalid SIM" If i try these same SIMs on my Nexus One, they all work and enable all communication functions including tethering. I called T-Mobile and they say that they gave me an unlock code that works for the whole phone and they can do no more. I called Samsung and they say that T-Mobile has possibly put in a change to the code to control tethering and charge for it. This bit of code stops me from using the tethering internationally. Then i called back T-Mobile and they say the only change they made was to add some bloatware and nothing more. With this run around, i am stuck. What can i do to enable tethering with my many international SIM cards on this fantastic phone?