talked to an at&t rep and for whatever reason she was unable to provide what the default sim pin codes are for both my iP4s. i tried "1234", "0000", last four of ssn or my 10-digit number. -what we end up doing was lock the sim by entering random numbers. -then called from another phone line and she provided a PUK to unlock it. -then i was able to set my sim pin code. yes, you can also get the PUK online in your account, but it was coincidence for my that the online account system was in maintenance so i had to call. just thought i'd share.