Can a US t-mobile sim card be cut to fit into Unlocked iphone 4?

Yes I just did it to unlock my iPhone 4. My advice would be to get a noosey sim card cutter, its like a small hole puncher and cuts your card perfectly to fit right in, unless ur using gevey then you just have to cut a little bit more. Bur noosey is preferred among the sim cutting community, look it up