I have a Samsung Galaxy S3 and I want to change my service provider, but my phone is locked and i would like to unlock without having to pay fees. I have already disconnected my service… And my phone is Samsung Galaxy S3 SGH-T999V.
I tried everything that you guys said and it didn't work, so I dropped the phone and bought a new one, and guess my carrier Virgin Mobile wants to make me pay 50$ to unlock my old phone that I have since last year, so I'm stuck with it.. And when you are upgrading the phone, they tell you that downgrading is impossible.. after upgrading. So it didn't work!
If the phone is CDMA instead of GSM, the steps that were given to unlock the phone would not work. The method is for GSM phones only. Virgin Mobile, although may have a SIM card, works on CDMA signals. Sorry that it wasted your time, but at least you learned how to flash your phone. You can use the same method to install a rooted ROM so the phone could rooted.
Were you able to sort things out with downgrading, unlocking, and then updating your phone?
In on 4.1.1 and I get no fourth option either
in network menu. I will try diff 4.1.1 in a sec does anyone have the link to the proper one with the fourth option? Sgh t999 Tmobile us
You can try the one found here: http://galaxys3root.com/galaxy-s3-stock-firmware/, which would be this one: http://stockroms.net/file/GalaxyS3/SGH-T999/T999UVDMD5_T999TMBDMD5_TMB.zip. This is 4.1.2, but may work. I know that the higher versions would most likely not work.
If you wish to try another source, try here: http://www.sammobile.com/firmwares/1/?model=SGH-T999&pcode=TMB#firmware. You would have to register with the website before downloading the firmware, but they mention that the firmwares listed are official.
You can also go here: http://wccftech.com/unroot-t-mobile-galaxy-s3-and-restore-back-to-stock-firmware/ and underneath where it says "Unroot Samsung Galaxy S3 and revert it back to Stock firmware:", there are links to different stock firmware that you can download.
There is no guarantee that doing this would work, so if it doesn't, try calling your service provider and telling them that you are going to Europe or out of the country and wish to use the local services there. They may try to sell you international services, but decline and they should send you an email with the proper unlock code that works for your phone. They would most likely ask you the Android version and Baseband version you are using, so make note of it (Go into settings and then About Device) before calling. 9 times out of 10, calling for this reason would let you get a free official unlock code that is almost guaranteed to work with your phone.
Please go to the samsungis.com website mentioned above as it is a repository of SGH-T999V ROMs. There is 4.1.1 stock firmware to download there.
I went to (androidayos) and the only version available for my phone is 4.3 Jelly Bean
I tried what you've said, and it didn't work, so while trying to dowload it on my phone, it said that it's failed, meanwhile my phone was still on download mode and and plugged to the computer, so I unplogged it and I restarted the phone, but now it says; Firmware upgrade encountered an issue. Please select recovery mode in kies and try again... I tried to connect it to kies, and it doesn't work... so what should i do???
Try to install a different version of Android 4.1.1 from here: http://www.samsungis.com/Firmwares/SGH-T999V.html. Your phone is in what is called soft-brick, which means the wrong firmware or a corrupted firmware was installed. Odin would be the only way to fix it since you are down-grading your phone, not updating, and the firmware is not running properly on your phone. Don't worry, this is not a big deal and can easily be fixed. When you want to upgrade, you can use the 4.3 version and upgrade through Odin if you would like.
You can review the information here: http://www.androidpit.com/how-to-downgrade-galaxy-s3. It has the Odin software you can download, but you have to find the proper Android 4.1 version for your phone. Here you can find Android 4.1.1 to "update" your phone, then go through the setup (skip through most of the steps since you will upgrade to the latest 4.3 anyways), then go through the unlocking process. You then should have an unlocked phone, then you can perform the OTA (over-the-air) update by going into the phone settings, selecting About Device, and clicking on Software Update. Otherwise, use Samsung Kies to update the phone to the latest version.
I can confirm the method Jan suggests. I used the instructions here: http://slickdeals.net/f/5620682-free-unlock-for-samsung-galaxy-s3-and-note-2-all-gsm? and there are credits to the XDA devs that mentioned this to work with all GSM versions of Galaxy S3's and Galaxy Note 2's. As a note, though, the updated Android versions may not allow the unlock code to work, but if it does work, you would not have to reenter the code even after a factory or data reset.
launch the phone app and press *#197328640#
In the Main Menu navigate to:
 Debug Screen
 Phone Control
 Network Lock
use Option Perso SHA256 OFF
wait about 30 seconds, then go back one step by pressing the Menu button then select Back, now you are in
 Network Lock
 NW Lock NV Data INITIALLIZ
wait for a minute then reboot your phone
If your device came with a branded firmware you might have to manually input certain settings e.g. APN for the new provider.
My android version is 4.3 Jelly Bean and it doesn't work. Like when I use option SHA256=>OFF , I wait for the 30 seconds and then I go back, but there's no ...
Unfortunately, you would have to use Odin with a downloaded official 4.1.1 Android for your phone, install this version, try the unlock method mentioned, then reinstall the latest version of android 4.3 that you are now running. You would lose all of the information on your phone when doing this, so backup everything that you can before trying. Otherwise, call your service provider and tell them that you are going to a different country and wish to unlock the phone to use a local SIM card since it would be cheaper. Many times they would give you the unlock code for free.
Yeah ok, but how can I do to pass from Android 4.3 to 4.1?