My complaints just get ignored

I rented a car from Europcar's Cape Town city branch during December for 10 days. About 2km from the branch I switched on the airconiditioner to find out that it didnt work. I turned around and started to return to the branch when the aircon came on so I continued on my way. During the course of the day to my great frustration the aircon continued to work intermittently. I phone the Europcar call centre to report this. They said that a replacement could only be arranged the following morning (it was a Sunday) as the branch I had collected from had already closed. I said that considering the aircon was faulty I shouldnt be charged for the first days rental and the Europcar representative agreed. Needless to say I returned the replacement car (I got the next day) after 10 days and was invoiced for the full length of time. I responded to the invoice email with my query but after 1 week no response has been forthcoming. In future I'll rent from one of those Rent A Cheepy places - Europcar provides poor quality cars (Europcar must have know aircon didnt work) just as they do and there is no service to speak of. Europcar website doesnt even have an email address for complaints.