Bad Customer Service. NO INVOICE FOR 10DAYS

Hired a car at Avis OR Tambo on the 11th April 2023 and was due for return on the 14th but then extended the rental to the 18th. Unfortunately I couldn't return the vehicle on the the date due to other commitments. On the 19th as I was about to drive to the airport to return the car, I got hjacked in vosloorus, I immediately tried to contact Avis but it took almost an hour to get through and report the incident as they kept transferring me to their voice call. The car was fortunately recovered by their recovery centre minutes after it was reported. I then called Avis OR Tambo on the 20th to report that the vehicle was ****** and recovered, I spoke to Mohammed, he advised he will call the investigating unit do a report then close the rental agreement. Till this day the rental is still open which contradicts their policy to invoice 48 to 72 hours after the vehicle has been returned. It's been over 10days since the car was recovered and I have not received an invoice. I called the customer care and I was advised to call OR Tambo directly to close the rental. I have been trying to contact the branch since the 26th April but I can't get through, the calls keep cutting off or just go back to their voice call. I am frustrated as I have other bills to pay but I put them on hold so I can settle their invoice. This is unprofessional and impractical business practices. Avis does not care about their customer services.