I booked a flight from Seattle to Paris for June 10th with Air France, but realized I could not make the flight. I called the customer service of the airline because I wanted to re-book my flight, which I successfully did!
The customer service representative informed me that the total fee for re-booking (150 euros or ~168$) + the difference in price of the two different flights (the new one on August 20th - my original one on June 10th of 106 $) would be charged to my account.
Surprisingly, I found that I was charged 274$ on the date I called customer service and an additional 320$ two days after the flight. When I called customer service I found out (after more than half an hour of waiting on the line) that the 320$ was for fuel surcharge.
First, I wasn't informed initially about this additional cost that was charged on my credit card. Second, I just read that this fuel surcharge is a bit of a lame excuse from the airline companies to charge you more for the fare (a fact which is not bothersome by itself, but why wouldn't this fee be covered by the cancellation fee?).
The main question would be if I can do anything to get my money back.
UPDATE: It was indeed a mistake and I was not charged in the end the $320. I am glad I called the customer service and called them up on that. Thank you for the answers!!