Customer service is unreachable

We booked a Toyota Highlander, but HERTZ gave us a Hyundai Tucson. The rental prices for these two cars are very different.

Forced to pay for vehicle upgrade, and directly upgraded to a 7-seater.

Picking up and returning the car at Melbourne airport was very smooth. The staff at the pick-up were very friendly and provided detailed and professional explanations of various scenarios. Their service was attentive, thoughtful, and very considerate.

The car was good. Although it was the specified model, we got upgraded to a Mitsubishi SUV at the store. The service staff were very friendly. We rented a child seat, which was quite spacious, so it was still cramped for a family of five. The on-site charges were about $40 more than the price listed on the rental website. There were many items listed, likely fees and not taxes! But I still don't understand why. When asked, customer service said it's the $75 child seat tax. Do you assume customers don't understand English?!