In what country did the rental originate? Did you receive a rental agreement when you picked up the vehicle? If so, what rate was shown at that time?

When you reserved the vehicle initially, was the rate "guaranteed" or "subject to change"?

Doing a chargeback with a rental-car company can be risky. The company might decide that they don't want you as a customer and put you on their do-not-rent list. Asking for arbitration under the terms of the rental agreement might be safer, as long as you have a legitimate case. Hertz arbitration option discussed in this thread:

Hertz arbitration to avoid rental car scams

Edited to add: If you are not a U.S. resident, I'm not sure if arbitration is an option for you.