Looks like T-mobile USA is looking to add more to the 1 million iPhone users it claims to have running on their network by selling micro sims to iPhone 4 users running around with unlocked iPhone 4’s. Currently T-Mobile running iPhone’s can’t run 3G or 4G on T-mobile but edge works fine. This could lead to maybe an iPhone 5 or a future iPad running on T-Mobile in the future. Currently T-Mobile says the sim will cost $10 but you can get them free online.
T-mobile offers micro sim card to iPhone 4 users.
uApps 