I had the worst ever experience at the Phuket Airport Hertz desk. I made a booking early Jan 2013 and the day before arrival (Feb), I was sent a reminder email by them of the confirmed booking. When I arrived at Phuket to my horror I was told there was no car available and I was to wait an hour for cars to be returned. While I was having breakfast I received a call saying a car was available. Having eaten quickly I went to the desk and was told they gave the car to another customer!! They then returned me the paper work with the word cancelled on it saying they cancelled by booking!! This is not the kind of service you expect from an international organisation!!
I was then told that they had organised a car for me with another car rental company and they would drive me there. I was driven to a back lane and to an unknown car rental company. I was left there to negotiate the rental of the car. Hertz did nothing that they claimed to have done for a replacement car. Basically they left me to sort out the mess they created.
As an international traveller I have never ever been treated so badly by a so called reputable car rental company! The reason why I went with Hertz was because they are supposed to be reliable. Evidently they are not and they have shown to be highly unreliable, rude, offer only poor service.
So my advice to you if you plan to rent a car in Phuket at the airport, go Avis, Budget, National - just NOT Hertz.