I bought an Iphone4 in NewYork last September, where I activated it with an At&T prepaid sim as i was on my way back to Taipei,Taiwan where I currently reside. I was using my iPhone here in Taiwan from that September to January. I traveled to my country of origin which is St.Kitts-Nevis Within the Caribbean, West Indies in January 2012. While there I did an upgrade of my iPhone4 to the software ios5.0.1. It asked me to reboot with the sim I got the phone with, I did so which was the prepaod At&t sim I bought when I bought the iPhone. Ever since the upgrade my phone has kept saying invalid sim no matter which sim I use.
I took my phone to the Apple store in Grand Central station, while I was in New York in February 17th, 2012 again on my way back to Taipei, Taiwan. The young lady at the store took the phone back to the factory settings, and said she repared it then she told me that once I get back to Taipei the phone company should issue to me a new sim and it will work. While there a friend of mine gave me her At&t sim from her iPhone4 to see if it was working and when she inserted it, it did work.
I have been back in Taipei for 3 weeks already and I am still unable to use my phone as it still says 'INVALID SIM" and no matter who I take the phone to they said they can't do anything about it.
I am now writing to you, soliciting your assistance with this matter seeing the sim got locked with your sim and I really don't know what else to do. My phone is not 1 year yet and I cannot use it where I reside. Lastly when i go into my settings it says Network Not Available, Version 5.0.1 (9A405) Carrier AT&T 11.0, ICCID No SIM. Please help in rectifying this matter as I don't know what else to do to get my phone functional again.
It seems as if its locked to AT&T now. At&t can't help you at all. Was it jail broken or factory unlocked? You need to speak to apple if it was factory unlocked. If it was jail broken then no one will do anything
*I am an AT&T employee and the postings on this site are my own and don't necessarily represent AT&T's position, strategies or opinions.
Given that it was working until the point that you updated the software, it sounds like the phone was a locked AT&T phone that was unlocked only because it was hacked (jailbroken) by someone. Updating the software wipes out the hack and locks it back to AT&T, which is it's original state.
Neither AT&T nor Apple unlock locked US iphones. You'll either have to sell it and buy a phone that works in your country or find someone else to hack it again (if it's even possible for that OS version).