I hired a car but the office was closed the day I went to collect it. I did not get my hire car.

Europcar entered into a legally-binding contract, took my money and then did not comply with its part of the agreement. I arrived at Carcassonne airport to collect a hire car but could not do so. When I rang to see when the office would open, the person who answered (a) firstly insisted that the office at Carcassonne Airport was open  (b) next said that Customer Services were the appropriate people to deal with my situation (c) then, when asked for their number, informed me that they were on holiday until the following day, and (d) finally, on discovering that telling me three times that it was 'impossible' for him to help in any way did not deter me from demanding help, he hung-up the telephone.
To compensate for this, EuropCar send an email which spelt my name incorrectly. In it I received a strings-attached offer of a £20 reduction on my next booking if paid for at 'the station' and an upgrade, 'subject to availability'. As I will require a car in June, I went onto EuropCar's website and got a price....... paying at the station would cost £14:50 more than paying in advance. So £20 off a future hire has an actual value of £5:50. Also, as any upgrade is conditional on availability, rendering such an offer potentially meaningless.
In my initial email, I asked for clarification of their policy with regard to answering telephone enquiries. That request was ignored. By way of deflection, their representative wrote that, regarding my conversation with one of the agents, they had sent feedback to all relevant departments to prevent re-occurrence; re-occurrence of what?
So, to clarify, EuropCar firstly reneged on a legally-binding agreement and having done so, then treated me badly. To atone for this, a man with a different name was offered £5:50.
EuropCar uses both the concept and the term 'Customer Service' in a way with which I am unfamiliar.