Submit instead of Next

I'm using a single step checkout. I tried to change the button from Next to Submit using the language settings, both override and and the main language settings because I'm using 1.7. How do I change this button?

If I wanted a multiple step checkout, how would I keep the other buttons as next, and the last button as submit?

You can do as explained there then:
www.hikashop.com/en/support/forum/4-how-...bel-next-button.html