i had this "SIM NOT VALID" issue the first day and they swapped the phone for a new one and it worked fine until i did a full restore on ios then i got the error again, apple didnt fix it they just swapped for a new phone, which worked until i updated the software, and once again they didnt fix it, they just swapped for new one, which worked until i needed to a restore. I called apple today and they said they will look into it and get back to me within 4 hours, but i see a lot of people called apple back in september and were able to restore their phones and have it work, could someone please tell me or email me EXACTLY what apple did to fix the issue so i can tell them, and preferably a ticket or case number i can provide them so they can look up EXACTLY how to fix it
Are you doing this with 7.1 Beta? If so there is an issue with the Beta same thing happened to me.