Default My Samsung Galaxy Grand 19082 won't update its software!!

Hello guys,

When I go to Settings>About device>Software update>Update ... I get this message "The latest updates have already been installed" !

it's 4.1.2 Jelly Bean... I know many people whom upgraded their Grand's by this method!! but my mobile doesn't work!!

I tried to upgrade it using 'Kies' it staid 4.1.2 !...

How to fix it and upgrade to 4.2??

Thanks a lot!