Another thing to check is what Premium plan were you on? When you downgrade to Basic you actually stay as a Premium member until your billing date. So if you were on the quarterly plan, say, you may still be considered a Premium member. The easiest way to figure that out is if you're still getting the weekly stipend.
If you can't see any land holdings on the web site, I'd recommend going to World > My Land Holdings in your viewer menu. Your menu may be a little different, of course, depending on your viewer, but that should show you what you are paying for.
Good luck!