I remember a while back, it used to be that only AT&T or unlocked models would work on T-Mobile, but only on their 2G network. Later on, T-Mobile did some infrastructure changes that would allow some older iPhones to work on their 3G (and maybe 4G?) networks. I'm wondering which iPhone models would work on their 3G and/or 4G networks, and if it involves any sketchy trickery to enable, apart from unlocking the phone. Thanks!