The actual supplier was Europcar. We arrived at 6:30 AM, and there was no one at the airport counter. We had to go to the office outside. (I guess it was because it was Sunday morning, and only Hertz had someone at the counter. Because of this, I will definitely rent from Hertz next time.) We paid half of the fee online and the other half at the store. The staff was not very familiar with the fees and overcharged us. Luckily, I had saved the receipt and got it corrected by showing it to them. When we returned the car at 2:30 PM, a few hours before our flight, no one was at the airport counter again. We had to leave the keys in their designated box. A few days later, they sent us a message asking for an extra AUD 400 for late return. Fortunately, I had taken photos and I'm now waiting for their response. If they continue to be unreasonable, I will fight for my rights. I advise everyone to take photos before returning the car, including the fuel gauge and the car's exterior, to avoid unnecessary issues.

No staff at the airport counter, had to find the parking lot by myself

The company didn't provide assistance after the vehicle broke down and kept passing the responsibility around.