Shocking experience with Hertz

We rented a car in Italy and were quoted an all inclusive price. When our credit card was charged it was a totally different and higher amount. I have now been trying for 3 weeks to find out why, countless calls and emails (to which i get a return mail with a reference number and saying you will be answered in 3-5 days) and still nothing. It is ridiculous and borders on theft. Why wont Hertz respond???????