Yes, this phone is locked for two carriers:
AT&T USA (GSM). This version requests the unlock code. SIM card network PIN.
Sprint and Boost Mobile (CDMA) carriers does not request unlock code and must be unlocked through software connecting the device to the computer by USB cable.
SM-G892A AT&T model from United States
SM-G892U Sprint and Boost Mobile model from United States
1. - Turn on the handset on with a SIM card not accepted by the device (your new network operator)
2. - If the card has a PIN number, enter it and press OK.
3. - The device will prompt: “Network lock”, Now enter the code and press OK.
4. - Your phone will indicate: "The operation was successful", becoming permanently unlocked.
Unfreeze code: If the code in step 3 does not work, type the secondary code and press Unlock, the phone will indicate Unlock fail, now dial the code again from step 3.
Device Unlock app method:
1. - Make sure you have an active data connection via mobile data or Wi-Fi.
2.- From the Application list, tap Device Unlock, the application is pre installed in your device.
3.- Choose the Permanent Unlock.
4.- Restart the device.
"Simple process with clear inductions. Unlock code worked perfectly."