CarFlexi - Risky, Unreliable and Disappointing

I booked a car through CarFlexi with Europcar. I received confirmation and an E-voucher, but when we arrived at our destination, there was no record of our car rental on the Europcar system. Our only option was to rent another much more expensive car, as the class of car that we booked was "sold out". I paid a deposit to CarFlexi for this rental. I informed CarFlexi of the incident and asked for a refund. I've sent three email requests this week, but they have not responded at all. From now on I will only book directly with the rental companies. Something like this can spoil your entire holiday.