I've never been charged a cent for phone booking and about 30-40% of my SAS tickets have to be broke don the phone because of their terrible website. I'm not sure what the official rules are, though I'm certain someone will post them.

Either because of Diamond or when you want to book itineraries that you can't get on the website they don't charge a booking fee.

Nevertheless, if you don't mind calling in and you can avoid the Scandinavians, the process is smooth and efficient as long as you know what you want and type in your EB number when you call (they'll ask for it).