AVIS - definitely not trying harder

I rented a car from Avis while my car was repaired. They debited my credit card with a 'deposit', promising to refund me within 30 days of the car's return. Then I received a notification of a traffic fine, but no other information. Then a debit of R 335.00 with no explanation (but not for the same amount of the unsubstantiated fine). And no refund. I have sent 4 emails to Avis and only received an automatic response. Appalling service,