Prevent Entityform Duplicate Submissions
You can try the Hide Submit moddule:


  Some users accidentally click the submit button more than once while
  waiting for their post to be saved. In some cases this may result
  duplicate postings or duplicate e-commerce orders.
  
  There are few ideas on how to solve duplicate postings but none is
  perfect. One of the solutions is a bit of jQuery to hide or disable
  the submit button after it has been clicked and replace it with an
  informative text such as "Processing..." .
  
  This module wraps that jQuery code and provides some options. Of
  course this, too, is not a perfect solution as it requires Javascript
  to be enabled. For browsers with Javascript disabled this module will
  have no effect at all.