Custom Permalinks

Pages are hierarchical, so that’s normal behavior. Permalinks are for posts (pages and posts are the same, but they’re not :).

I take it from your post that perhaps you have your site set up so the front page displays a static page (set in Settings->Reading), and the name of that page is “sample-pages.” So, if you set the parent page of your test page to be sample-pages, then you will get the URL you have described due to the hierarchical nature of pages.