Hello @Michele754,
Some time ago Airbnb changed their fee policy to all charging a greater percentage the stricter the cancellation policy chosen by the host. Perhaps this may explain the unexpected rate.
To see information on ways to contact Airbnb support to discuss the issue type "contact airbnb" in the "Search the community" box on these forum pages where you posted your question. Scroll down a little in the list of suggestions that appears and click on the "Contact Airbnb: A Community Help Guide[UPDATED]" one. That lists phone numbers and ways to contact them via Twitter or Facebook.
Steve.