We booked the car for a week but our plans changed so we tried to modify the booking prior to arriving. We were unable to modify the reservation. When we arrived at the airport we were told they could not modify the reservation for us but it could be done when we returned the car. The car was dirty and smelled of cigarette smoke. The next day we tried to return the car and there was a line of people all the way to the baggage claim (only at Avis, not a single person in line at any of the other car rental counters). I waited in line as long as I could, it was barely moving, and my husband was calling from the terminal there were police everywhere and he was not allowed to wait for me any longer. I went to the front of the line looking for a key drop box. There wasn't one so I handed the key to the rep who was with another customer. We arrived home and called Kayak and Avis to get the charge refunded from the credit card. One rep hung up on us. Both companies told us it was the other company who was responsible for refunding us and nothing could be done to modify the reservation now. Only at that counter when returning. Ridiculous. After wasting at least 2 hours of our time and ruining our morning plans we finally got an answer that we would be charged nearly $300 for less than 24 hours of using this smelly, dirty, Kia vehicle. The rep was unable to tell us what the breakdown was for these charges and we would get a receipt emailed to us from Avis with the breakdown of the charges, which never arrived (shocker). The WORST car rental experience we have EVER had. We book from that airport all of the time -- never a single problem changing our reservation with the other car rental places. We will NEVER EVER use Avis again. THE WORST CUSTOMER SERVICE EVER. They shouldn't even be in business SHAMEFUL