The important thing to know is that you don't have to pay for EC, but at times the website and kiosks might make it look like you do. If EC seats open up and are the only option, just refuse to select them. As someone else said, you'll get a gate pass to use to go through security and then at the gate you'll be assigned a seat right before departure. You might even get assigned EC for free at that point (and only that point).