They can do it.. I have recently done unlock for one which was denied by ATT.. but make sure that you get the one which says 100% for blacklisted and all those.. Coz there might be some cases when you cannot unlock from the normal service. I tried the normal service which they said denied by ATT.. but later it was unlocked by their premium service. I really didn't bother to know whether they are trying to make more money out of it.. But i was happy that my phone got unlocked. If you SIM is blacklisted, you can still unlock it.. worst case you won't be able to use in US.. but majjale Nepal ma chalcha..