AVIS CAR RENTAL

We have had the worst experience with AVIS ever! first they wont give us a car that we have pre booked and payed for when we land at an airport at 22:00pm when we ask for a manager to be called they refuse and now we have been waiting for almost a month for our refund every single time I phone they say that no refund has been booked and someone will contact me BUT NO ONE EVER DOES!