No refund on Cancellation

I booked a car through [URL Removed] for one day in Dec 2015. The supplier they used was Avis, Port Elizabeth. Unfortunately I had to cancel the booking. As the only number (other than an international one) was given on the booking confirmation email, was the PE Avis number, I contacted them to cancel and was assured by the person I spoke to that the booking was cancelled and I would receive a refund in 4 - 5 days. I have never used [URL Removed] before and the details of how to cancel a booking was nowhere on the email confirmation sent to me. I therefore took Avis' word that the booking was cancelled. However, they did not inform [URL Removed] that the booking was cancelled - neither did they inform me that I had to cancel through them and not Avis. Therefore, according to the terms and conditions (somewhere on the [URL Removed] site), I have become liable for the rental of a car that I never used and have been refused a refund. I am not sure whether to complain against Avis or [URL Removed] Cancellation details should be made far more clearly known. I feel totally ********** by both of these companies. Avis refused to assist and passed the buck onto Rentalcars.