Why won't my server properties change anything?

I've recently been playing minecraft with my cousins and I set it to easy mode and it worked. Now I'm trying to switch it back to peaceful mode and it isn't doing anything. I saved my server properties while the server was closed and when I open it, it is still on easy. Can anybody help?

Server.properties should keep settings if you save it.
If you delete server.properties. Run the server and it will replace server.properties.

These commands can be used in game:

difficulty peaceful | easy | normal | hard

Changes the difficulty for as long as the server is running. If the server is restarted, the difficulty will go back to whatever difficulty is set in server.properties. The difficulties can be abbreviated to "p/e/n/h" or "0/1/2/3" respectively.

gamemode <survival | creative | adventure | spectator> [playername]

Changes the game mode for playername. The game modes can be abbreviated to "s/c/a/sp" or "0/1/2/3" respectively. If no playername is given, it will set your own gamemode. Remember, this will only affect playername and no one else.

Hope it helps.