Hi there. Neurotic non-jailbreaker here, pretty sure I shot myself in the foot with my old iPhone 3GS and I am turning to you fine people for help. I have Googled high and low and tried many different things, none of which have worked and now I am at my wit's end. Allow me to explain: I had lent my old 3GS to a friend years ago (old bootrom). Back then, I used redsn0w to jailbreak and unlock it, installing the iPad 06.15.00 baseband in the process so he could use it on T-Mobile. Now, 4 years later, I finally got the phone back from him. Curious to see what was on my phone back in 2012, I decided to restore it to my backup in iTunes that I had made before we jailbroke it. Of course the software was well out of date, so I updated it to the most recent firmware via iTunes, iOS 6.1.6. This was where I went WRONG. Upon the phone coming out of the firmware update, iTunes says that there is no SIM card installed in the iPhone and that I can not activate it. I had tried my old SIM and even placed my current 6S SIM in an adapter to no avail. I delved into the realm of Google-troubleshooting, and eventually I determined that since I had the iPad baseband installed, I have corrupted the firmware because I upgraded it via iTunes. Like I said, non-jailbreaker here--had no clue. Thus far I have tried every potential fix that I have come across, none of which have worked. I fear the problem is that redsn0w didn't support 6.1.6 and can't communicate baseband downgrade to my device. It typically returns an error of USB communication problem. I feel like I may be stuck in between a rock and a hard place and because the device is so old, my chances of finding someone who can guide me through this is slim. All I want to be able to do is get my old data back on there so I can put the phone away and pull it out one day and reminisce. Someone taking the time to troubleshoot this with me would be so greatly appreciated!