This is Sixt and Hotwire.com's idea of a car with room for 3 suitcases

On Sept 5th I showed up at a Sixt branch in Florence, Italy to pick up a car I had reserved through Hotwire.com one day earlier for return on Sept 8th. The booking was for an "Economy vehicle seating four people and with enough space for 3 suitcases" as shown in the attached confirmation from the travel site. The car shown in the category was a 4-door Ford Fiesta sedan. 

You can imagine my surprise when they brought me a very small Fiat Panda. I did ask the person in charge if there was something bigger within the category and she said no, handed me the keys and walked back to the office. I took the keys and figured I could swap the car at another Sixt location on the way to Milan. I thought this had to be a mistake.

So I went back to the hotel, picked up the family, miraculously fitting everything and everyone in the car, and hit the road. Later in the day we stopped at another Sixt branch. This one was in a gas station in Modena and, even though it was technically open, the person in charge was not there. We managed to get someone from Sixt on the phone but all he said was "please wait for my colleague to arrive". We did wait for over 30 minutes to no avail, so we decided to go back on the road since there was still a long way ahead.

We made it to our destination that night safely but very uncomfortably. I personally wrote emails to Sixt and to Hotwire.com the next day. All I got from Sixt was an automatic reply, and hotwire.com's answer was basically: "Tough luck, the rental company is allowed to give you a different car than advertised". 

Now I completely understand that there is no commitment from the rental agency to provide the exact same make, year, color and model advertised online. All I was asking was a car *** in the category that I chose and partially paid for *** on Hotwire.com. Something that would fit the 4-adult, 3-suitcase description. Please take a look at the above picture, the Panda is not a 3-suitcase car, and it's not in the same category as the Ford Fiesta pictured in the Hotwire.com reservation (please see attached pdf file).