Samsung Galaxy S5 AU SCL23 Japan version. Help needed to unlock etc

Hey guys. I just got a new Samsung Galaxy S5 AU SCL23 Japan version off ebay. It was sold as unlocked but it wont recognize any sims. I am a noob and made a bad purchase. I know nothing about smart phones, rooting and roms etc and I was told this is the place to learn. I tried to root it with an online guide but could not get the menu up.

I wont be happy with rooting alone as even when I set the phone from Japanese to English the interface is still pretty bad with Japanese characters all over the place.

Are there other options to kind of "format" all the old network branding etc off the phone and just run a regular non Japanese biased style Android OS?

Or should I just send it back and hope I get the money back?

Thanks guys.