A stark warning about the above - avoid making the same mistake as me.
I booked a car from these people from "Rome Fiumicino Airport", believing (understandably) this would be convenient for my flight. What they neglect to tell you is that they are in fact several kilometres away from the airport, and offer a very limited shuttle bus to the airport, at times that suit them and not you (it is certainly not 24 hour or even close).
We nearly missed our flight having to deal with navigating our way to their offices, and then waiting for ths shuttle bus when it eventually turned up late.
I simply do not understand how, given the critical nature of timing around getting to an airport, they can claim they are based at the airport. If you want the convenience of an airport-based car rental service, avoid Advantage.