Poor service

The car that was rented out to me is due for service. Now I called Avis Margate to exchange the car, I spoke to Siya and I requested him to make reservations for me to collect the car from Avis King Shaka international Airport. When I arrive there, no reservations were made, and they said the was overdue. They couldn't exchange the car because they are saying my insurance was supposed to extend the car on their Portal and not send Avis an email!! I am so frustrated as I am far away from home!!!