You'll need to provide a bit more information. Things that might be relevant:

* Is this an unlocked international phone, one sold through a SA carrier, or an import from another country? Different versions get different updates, and a carrier-branded version may not get updates when used on another carrier.

* What OS version/software build are you on anyway? It may be that you already have the most recent for your particular S6 model.

You could also check at sammobile.com to see what the latest update for your model is. You'll need the full model number (not just "S6"). It's possible to download firmware from there and install it, but I've never done this so am not the person to ask for instructions (a search should find them easily enough).