Show message to users that try to change settings that wont be saved

I've "inherited" a Drupal site that uses Feedapi. The site was configured to update existing items and I'm trying to turn that off. It seems however that when I uncheck the "Update existing feed items." box and save the settings for the content type everything seems to be working fine but when I go back into the content type nothing has changed.

It could be that this problem is not with the Feedapi but rather a collision with something else but I'm posting here in case someone has had the same problem with nodes that gets updated although set not to.