Rented car

Hi. I rented a car from Avis through my insurance. They asked for a R2000 deposit, which I paid. When it was time to return the car. I called Avis twice, asking them to come and collect the car and on both occasions, they said they are on their way. They collected the car the following day. Now I was refunded R1700. When I enquired, they said they charged me for an extra day. Of which is the day, they did not come to collect the car. Now I have been trying to follow up and I was put on hold for over 20 minutes. Their service is very poor.