Customize Completion Page

Hello, how do I customize the completion page? After I submit and successfully complete the transaction, it comes back with a page that says:

Complete
Your order number is 1.
You can view your order on your account page when logged in.

I want to edit this text. For starters, I don't let people make accounts, so this text would be confusing to them.

I went to /admin/commerce/config/checkout-flows, edited Default, and edited Completion Message and saved. But when I go to complete a checkout again, it gives the original default message quoted above.

Edit: For now, I enabled String Overrides module and was able to edit the text using that.