Can I book and car???

Servus, I am trying for days now to book a car for my upcoming trip on the website. It keeps on saying the session has timed out. Forget to call the call center they does not exits. Question does AVIS exits? How can I get a car book for my trip????? Before you say use this browser and that browser, re-boot your PC etc., no! We are tech savvy so do not even start with that! I just want to book a car in Windhoek at the airport? Is that so difficult? Danke