I have had multiple issues with Hertz rentals in Europe over the past years (grossly exaggerated damage charges, undisclosed dynamic currency conversion at very unfavorable rates, etc). My contacts with Hertz corporate in the US and customer service in France were less than satisfying. However I escalated to Hertz International by first emailing Michel Taride with a response from his Executive Assistant Lynn Perrini (email@example.com) who the sent me to Barry Cooney at Hertz Executive Customer services in the UK or Ireland (CRDUKONE@hertz.com)who was very responsive. In the 2014 case it took over 4 months to get a satisfactory outcome but in 2016 I went directly to him and was immediately reimbursed for the bogus charges. I do not know if they are both still at Hertz International but I would suggest that you try them.