Europcar International review: Poor service

I pre paid for an automatic car as I just had ankle surgery and was unable to drive a manual car, pick up time was 4:30 pm on the 19th of august. They close at 5pm. We tried to call repeatedly to let them know of our flight delay, all we got as answering machine every time long before they closed. I was told they helped other people off the same flight late at night, i'm guessing that for them they did pick up the phone, it even says on our booking form "if your flight is delayed we will save your car for you" the very nexy morning I called to pick up my pre paid car, I was told they gave it away to someone else as they assumed I wasn't coming...? No one called me to check at 4:30 the previous day if I were coming or not, why not call me and ask? I was stranded, all the way from california and the reason I pre paid it was so that it would be there for sure when I got there, not reserved it paid for it!
They called me back in the morning and said someone coincidently had just dropped of a mercedes (the only automatic) and I could have that for an extra 50 quid a day... I want my original rental not a fancy mercedes. So I was penalized for their mistake... So now i'm 250.00 quid out of pocket simply because they couldn't pick up the phone and dial 12 or so digits? Their mistake so they should upgraded me at no charge, but no, they billed me... Shameful business practices, and when I got their that car was stone cold so was it just dropped off? Or was it there all the time... Who knows... All I know is a paid for an employees laziness in making a phone call... I'm expecting a refund for your error not mine...