Software update

My iPhone is a 6S plus… I am trying to update 13.0, which is allowed on this phone. On my update, it says I am up-to-date with 12.5.1… Which is not true. When I go to software update, it won’t list 13.0… And I desperately need to download it. I’ve tried many ways, but 13.0 won’t show up so I can download it. Any suggestions?