You can uninstall Evercontact directly within your domain's Evercontact settings as you see in the bottom right here.  One click, and you're done! Afterwards, please do leave us a bit of feedback on why you decided to leave.  Thanks!

Alternatively, go to your google apps domain admin console & click on "apps".

Click on marketplace apps

Click on Evercontact

Click on the trash can icon in the top right.

And then click "remove app".