[AT&T, Rogers, Bell, Telus Samsung Galaxy S III] licid:
Hello everyone!

I am not big on joining websites but I felt after everything that I had tried and experimented with, I needed to get the word out to possibly help others, or at least provide some insight. I am unable to post to the thread in question as I am considered a n00b so I am posting in the general section. If this doesn't belong here, I apologize in advance.

I recently came across this thread after finding out I corrupted my IMEI number.I have a Galaxy S 3 through AT&T. To make a long story short, I never backed up my original IMEI and rooted the same day following this procedure right after I got the phone. Shortly after I flashed a few different roms (aristdemos and black jelly to name a few). All was good until I wanted to go back to stock and not use a rom anymore. Thats when I noticed my IMEI was showing as 0/0 . Unfortunately, I do not know at what point I lost my IMEI, whether it was cwm or flashing a rom etc... After some digging around, I was able to inject my IMEI number back into my phone using the RF NV Item Manager program. My IMEI was now showing the correct number (per the back of my phone). After I did this, I was able to get LTE signal but would constantly drop in and out of EDGE as well. I was also unable to connect to my microcell anymore, it would connect for about a minute or two, then drop and would never connect again until a reboot. At this point I had good signal (full bars). I put my sim card into my iPhone 4 (previous phone) and the iPhone connected to my microcell right away, no problems so this ruled out the sim. Speed tests would only pull in 5-10 Mbps with full bars on LTE. I am in Cleveland and normally it should be doing 30-50Mbps. At this point I felt there was a data issue as I was able to make and receive calls and send/receive texts. I tried different roms as well as stock with no root and all produced the same results, poor data issues. At this point, I then I followed the 3rd post procedure about creating a QCN file and restoring it to the phone. This was the tipping point of no return. After restoring the QCN file I generated my phone would constantly be stuck in EDGE. Only a reboot would bring back LTE and even then it would only stay on LTE for no more than 5 minutes and drop back into EDGE. Once on EDGE it would not come off EDGE unless the phone was rebooted. I am in downtown Cleveland and there is LTE here so I know it was not a coverage issue. After scouring these threads and trying everything I could think of that people were suggesting in posts, I ended up with no success. I flashed to stock and took it to the AT&T store (I am still in the 30 day window) and had it replaced. I now have LTE all the time and it also connects to the microcell with no issues. The first thing I did was backup my IMEI when I got home. I feel that there is something else in NV ram or maybe the efs partition that holds other info about data settings as injecting the IMEI was not enough.

I hope this helps or at least points you in the right direction if you corrupted your IMEI and are having data issues. I know that taking it to AT&T is probably not an option for everyone either. I guess its also possible the phone was a lemmon but I just wanted to share my experience with you all.

Happy fixing your data issues!