I found the same thing today, but found the solution…
1. Go to the page you wish to edit.
2. Click on “Screen Options” from the top right of the page
3. Check the boxes for “Discussion” and “Comments”
4. Update Page
5. Scroll to the bottom of the page, you should now see a section called “Discussion”
6. Un-Check “Allow Comments” and “Allow trackbacks and pingbacks”
7. Update Page