General Channel in Org-Wide Team

I setup an Org-Wide channel and turned off everything.  I unchecked every box in Member Permissions, Guest permissions and @mentions. In the Channel Settings I have it set to "Only Owners can post messages".  However over the past week I've have 7 posts from people who are NOT Owners (triple checked this).  How is this possible?  They should not be allowed to post given that everything is turned off but yet they are posting for the entire company to see.