Horrible experience at Avis Cape Town International Airport

I scheduled a booking and paid via FNB ebucks, flew from OR Tambo International Airport to Cape Town International. Stood in line to pay and collect the vehicle but instead I was refused and no reason was given. I had the most humiliating experience at Avis Cape Town International Airport, I requested supervisor intervention but still no reason or information was given. Why did they accept my booking only to embarrass me at the last moment. What is it that I owe them or done wrong that they don't even have the decency or audacity to reveal. I tried to make a separate arrangement via my wife, but they refused to take any payment from me. Avis is disgusting and their service is shameful!!!! I tried to lay a complained but the agent on the phone dropped the phone in my ear! One cant put trust on AVIS.... they treat people like ********* and a word to describe them is yet to be found.