I got an iPhone from a friend who says that the phone is unlocked, but every sim card I try in it seems not to work, it keeps on coming up with the same message that "There is no SIM card installed in the iPhone you are attempting to activate. Please disconnect and insert a SIM card in the iPhone." when have clearly put one in.
What can I do?
См. статью: Why can I not use any sim card in my iPhone even though it is unlocked?