bad customer service and over-charged

We picked up a car in Bordeaux on May 31, 2012.  The next day we had a flat from a screw that made the tire uninflatable.  There was no spare tire!  After several failures to call us back when promised the next day, we finally borrowed a car from our hotel and went face to face with a Eurcar agent in War
at la Caneda.  At that point, we had been without a rental car for 24 hours with no prospect of getting another.  All Europcar agents would say is "it's not my fault - there's nothing that I can do.  There are no cars available for you".  No one even said that they were sorry!

Fortunately we were able to browbeat the agent in Sarlat into giving us a car although she said that she would be in trouble for doing so!

Subsequently Europcar charged us in full for our rental even though we did not have a car for 24 hours thanks to their totally disinterested service.  Their big concession was to subtract 10 Euro from our 135 Euro cost to rent a GPS for 4 days.!!! Totally unacceptable - I'd like all North American travel agents to be aware of this so they will not refer clients to Europcar ever again. Please advise if you are aware of how I could do this - E-mail me at janyceclark@bell.net - I don't want anyone else to be ripped off by Europcar.