I called the number on the email and they game me the customer service number. When I called the customer service number, and selected the option to cancel my account, and was redirected to http://www.efax.com/cancel.
When you go to that page, you have to select the "Chat Now. 24x7" button. Then you have to make your cancellation request via a web based chat session. (Make sure you answer the question about why you want to cancel fast enough, otherwise they will disconnect the chat, without canceling the account.)