content cannot be displayed in a frame

We set up a payment portal on our website about a month ago. It was working fine until last week and now we get messages from IE - To help protect the security of information you enter into this website, the publisher of this content does not allow it to be displayed in a frame. or from Chrome - simplecheckout.authorized.net refused to connect. I know that this has something to do with the iframe - Specifically, the webserver is setting the “X-Frame-Options” header to be “sameorigin”…can anyone help me fix this? I don’t write enough code to do much - I used the html code provided by the vendor to set up the page originally. Any help or direction would be greatly appreciated.