Turn off comments for Posts & Pages in Wordpress

Posts:
Settings >> Discussion >> remove the check from "Allow people to post comments on new articles"
Now what you have done only applies to new posts that you would publish from now on. To remove comments feature from previously published posts:
Posts - select them all and "Edit" under bulk actions and press apply - choose "do not allow" next to comments and hit update posts.
Pages:
Pages >> select them all and "Edit" under bulk actions and hit apply >> choose "do not allow" next to comments and hit update posts.