I have a Wordpress post in which I have disabled comments. It says “comments are closed”. However, I’m still receiving spam comments to that post. How is that possible?
no… “comments are closed” mean u can’t command on that post.
send me ur url, i’ll check them to review. 
I have the same.
Maybe when comments are closed it only means that comments form don’t show up on the site but when spammers use some spam script they can post comment.
Maybe you should delete comments template directly from php site?