Query about margins

I tried to adjust the margins of my page to something smaller than the default 10mm. I set all margins to 7mm. In the design and preview panes, the left and right margins have moved and I can drag stuff into the extra space, but the top and bottom margins are stuck on 10mm. ]
If I try and make the margins bigger, it works ok, but it won’t go below 10mm. What am I missing?

Double check the header and footer margins on your master page as well.

Worked perfectly. Thank you.