Do you want to completely get rid of the default WordPress comments? You may want to have a more professional look for your website as I did when I modified my friends Voices of East African Women Non-profit website by completely removing comments on pages and posts.
The best method that is always safe for me to do is just to go to the Appearance > Editor and find comments.php Comments (comments.php) and select all text then delete. This has worked for me on various themes because it is safer and easier than going to the Single.php post and looking for the php line that calls the comments.php. After you delete everything in comments.php, the singles.php file or whatever your theme calls the single posts php file will still call comments.php but the PHP won’t execute anything as it will be blank.
Some themes can get very complicated and you may have a difficult time finding where the comments are being called from so it is a wise idea to use this method that works very well for me.