Yes you can use Jio sim in samsung Galaxy J2 if you have a already activated sim then you can use it. Now a day all sims of Jio are coming activated.
First, step to download Shortcut master android application.
After download shortcut master simply install on your android device.
Now open this app and select engineering mode or service menu from the main menu.
Here find system app option if this option is not available then dial *#2263# from dailer app. Now Go To Key Input And Enter 0000 and Wait some times.
After that select System app option and you need to change LTE bands.
Now go to Select - Protocol - NAS - Network Control - Band Selection - LTE Band and select Band 40.
After that restart your 3G phone and enjoy reliance jio 4G sim in your 3G phone
