I have bought an unlocked iphone and instead of AT&T’s service I am using t-mobile service in my iphone. I know that t-mobile 3g network doesn’t use the same frequencies as AT&T’s, so I can face slower data speed in my t-mobile iphone 4. But I am curious to know that is there any way by which I can increase the data speed of 3g network in my t-mobile iphone 4?