HTC SDA (USA) / SP5m (Tornado)

I just bought an unlocked t-mobile sda. I am out of the states in Guam where we have no t mobile service. The phone works with our local GSM service fine but I cannot get wi fi to connect. It appears to connect but I.E. will not connect and I keep getting error messages. Does anyone know how to make this thing connect to any wifi network world wide??? I live in Vanuatu and want it to work there and Australia, etc.

Thanks