Need help please!

[AnJarBo]

Hi everyone. I'm having some serious (or at least I think so) problems with my I777. I live in Colombia, and I bought it over two years ago, had it shipped over by a friend, unlocked. Up until today I'd been using it normally, without any major problems.
However, the last couple of days it started behaving strangely, (turning itself off every once in a while, losing data, etc), so I decided to update my rom today.
I tried to install a new CyanogenMod 4.4 from this site, but I got some kind of status 7 error and it didn't behave properly after that.
Next thing I did to try to fix it was flash a stock JB 4.1.2 rom via Odin.
It worked, but that's when the major problem struck... Apparently my phone got locked for AT&T again or something. It's not recognizing my sim-card anymore. It shows the "no-sim" notification on the top bar, yet it also shows it has a signal (no data, just phone signal), even when my sim-card isn't inserted. When I go in the settings to try to access the mobile networks it says insert sim card even when it's in there.
I did a lot of searching and I used GalaxSimUnlock, which I got from this site too, and it confirms my phone is unlocked.

So basically... What the heck happened?? Is it possible that after three years of using it perfectly with my Colombian sim, the AT&T lock just "came back" or something after flashing a stock rom?

Any clue guys?

 

[pepe100]

If you used galaxsimunlock the unlock is permanent.

Sent from my SGH-I777 using XDA Free mobile app

 

[TheGeekyNimrod]

After you flashed back to stock, did you try to root again and flash another custom ROM?

I could be wrong on this, but the AT&T stock firmware may not be giving you the choice to register the SIM or change the APN settings for you particular network. I can't confirm this though as I never flash to stock long enough to actually use it. I always root and go back to something else immediately afterwards.

The only suggestion I have is to go back to a custom ROM and try again.

If you are trying to go to KitKat, be sure you have the newest compatible recovery (CWM or TWRP) as the versions of those that work with JB will not allow you to flash a KitKat ROM. There are plenty of threads that will tell you what versions you need. If it's an SGH-i777 model then all you should need to get the proper recovery is to flash one of the two KK compatible kernels as the recovery is packaged with them.

Good luck!