Worst service ever and incorrectly billed

I hired a car on the 3rd of April 2026 at 20h00, returned 20h55 on the 7th of April, I used the self check in to leave the key as they were closed, I included the petrol slip. On the 10th I called to check if everything is fine as I still did not recipient an invoice. Customer agent confirmed and sent N invoice with return date 08 April at 07h08 I requested they fix my invoice and check the footage. On the 16th I called back as I did not get rectified invoice neither the refund. Sent from pillar to post and nothing came out of that call. Today the 21st April 2 weeks from returning the car and lodged complaint, I called back again to check my refund and if whether my invoice was rectified. After holding 8 minutes for an agent that was supposed to assist, the call was answered by someone at branch level who refused to help and wanted to transfer me to Customer service again. Avis used to be a reputable car rental company but I have received the worst service ever.