Do you love your phone, but not your service provider? That's what happened to my girlfriend, who has been limping by with slow and spotty service from our corner of Los Angeles. When she upgraded her phone to the new Samsung Galaxy S4 she noticed she wasn't getting a serviceable or reliable connection, whether for voice or data. It was time to switch network providers, without purchasing a new phone. But first I needed to unlock her device so she could make the switch...
The Samsung Galaxy S4 is one of the best Android smartphones currently available, but on our local T-Mobile network we found the whip-fast specs hampered by buggy-slow network speeds (note: the network speeds could be wildly different just a few miles over, depending on specific network location and user load). Emily noticed I was rarely afflicted with the same issues as an AT&T Wireless subscriber, as we live close by one of their antennas; she decided to bite the bullet and pay the extra $10/month to switch networks (fortunately she wasn't bound by a contract).
The T-Mobile Galaxy S4 model (SGH-M919) is compatible with AT&T's network, and once carrier unlocked can be activated to use as an AT&T device (only caveat: sans LTE network). Carrier unlocking the phone not only opens up network provider options, but in case you decide to sell your phone, unlocked devices sell easier and at higher prices.
I discovered this easy to execute set of instructions over at XDA Developers, allowing any T-Mobile Galaxy S4 owner to unlock their device without the need to delve in the process of rooting the phone or change via software; everything is done easily through the built-in Android menu screens, barely more complex than inputting the Contra code:
- Go to phone dialer, and enter *#27663368378# for the debug service menu.
- In "Service Mode", select  UMTS
- In "UMTS MAIN MENU", select  DEBUG SCREEN
- In "DEBUG SCREEN", select  PHONE CONTROL
- In "PHONE CONTROL", select  NETWORK LOCK
- In "NETWORK LOCK", select  PERSO SHA256 OFF
It should show:
SHA256_OFF => SHA256_ON
- Now touch the first line SHA256_ENABLED_FLAG
It should show:
MENU NOT EXIST
PRESS BACK KEY
Current Command is 116631
- Now press the menu button and select "Back"
It should show:
SHA256_OFF => Not Change
- Again, press the menu button and select "Back", and you're back in the "NETWORK LOCK" screen
- Press the menu button and select "Back", and you're in the "PHONE CONTROL" screen
- Press the menu button and select "Back", and you're in the "DEBUG SCREEN" screen
- Finally, press the menu button and select "Back", and you're back in the "UMTS MAIN MENU" screen
- Select  COMMON
- In "COMMON" screen, select  NV REBUILD
Now you are in the "NV REBUILD" screen, you should see the following text:
You can Restore Cal/NV
- Now for the final step.
In "NV REBUILD" screen, select  Restore Back-up
The button lights for menu and back should come on, and the phone will auto reboot in a few seconds.
How do you know whether the unlock is successful? When successful, upon installing a AT&T SIM card, there will be no pop-up dialog asking for an unlock code. If the phone is unsuccessfully unlocked, an unlock code prompt will appear.
The unlock process took less than 5 minutes and worked perfectly; the next day we took in the unlocked S4 to a local AT&T Wireless retail shop where the phone was transferred to their network with a new SIM card without question or a hitch (we were told activating unlocked devices is now extremely common).
Please note, like any alteration to a phone, it's extremely advisable to backup all your information before attempting an unlock. The unlock is permanent and requires the device to be stock, so proceed with caution and do it at your own risk. For additional information, check out the XDA Developers forum
for further discussion and details.
(Image: Gregory Han; Kumer Oksana/Shutterstoock)