Avis trying to ***** my money

On the 21/08/2020 I hired a car from Sunninghill Avis, and I returned the car the following day 22/08/2020 at 15:30 and the agreement was to hire the car for 1 day and bring it back the before 16:30 and I adhered to the rules… On 26/08/2020 I downloaded the invoice and on the invoice I was billed for 3 days to the total value of R2245,57 plus R1980,24 I called the branch and I was told it would be sorted by 28/08/2020 but nothing, I then went to the branch on that very same Friday , the manager calculated and assured me it will be sorted. I sent an email to customer service and till date I have received about 4 incorrect invoices. R686, 25 was refunded probably from 1 of the many incorrect invoices and an amount of R3539,56 is still outstanding I am extremely disappointed at the treatment I am receiving from Avis, my first time hiring a car and I am billed for things I don’t know and its taking forever to resolve this issue while I suffer and my debit orders bounce. Can someone anyone please resolve my case, rental agreement number E***