You can email
[email protected]; you'll generally get a call back from someone at their headquarters in Connecticut in a week.
I've been booking through Priceline because they will price almost anything you can find on ITA Matrix. However, I had to call them because Air France cancelled a flight as part of a schedule change, and the phone operator cancelled my ticket and then tried to get me to agree to the cancellation -- she said "For this one, cancellation is best... do you agree to the cancellation sir?" about 10 times. Once I asked for a supervisor, the supervisor tried the same thing; I had to say "I paid Priceline for a ticket, I didn't agree to the cancellation, I feel that Priceline is obligated to get me to my destination" before she'd even try looking for alternates at all.
I came to this form to ask the question -- does anyone know a good real travel agent that will handle schedule changes for you? And what is it going to cost me?