Flash the combo modem. And unlock without root
Operation: Unlock
Selected model: SM-J120A
Software version: 28.8.1

Searching Samsung modem... detected COM23
Reading phone info... OK
Model: SM-J120A
AP version: J120AUCS3AQE1
CSC version: J120AATT3AQE1
CP version: J120AUCU3AQE1
Product code: SM2J120AZWCATT
Phone SN:
Unique number:
Reading IMEI... OK
IMEI: (SIGN: OK)
Reading data from phone... OK
Unlocking... OK
Rebooting phone... OK
Unlock done
download here
https://mega.nz/#!kdVGGIrI!FX47uEVd7...CMMhRDmz2zQ_Xs