NOTE: This procedure won't root the phone, it's a FIX to achieve the unlock on J3 updated to PD3 or above.
If your phone is on a lower Software Version than PD3 then proceed to unlock directly
. (Read this topic
if you don't know how to read the Software Version).
Our app will recognize if your phone needs this fix and will notify you it with a pop-up, if you don't see any pop-up when the app starts then you don't need this fix or you already applied it.
While if it is on PD3 or higher rom then you need to root it or downgrade to OL2. To downgrade it just download the OL2 rom from here:
SM-J320P Stock Official OL2 (5.1.1) Click to Download
Then use these instructions to flash it: How to flash a stock official binary tar.md5 file
You will be able to update the phone again after the unlock, using either the OTA (Over the air) update or Odin3, the phone will remain unlocked.