Avis is thrash!!!

I rented a vehicle at Avis, collected it from EL airport on 11 December 2020 at 08:30 and returned it on 13 December 2020 at 08:00.

I later received an invoice stating an amount that I apparently owe due to a damage on the vehicle. Fortunately I still had a copy of the inspection slip and the damage was recorded, so I queried and sent an email to the Branch Manager and the Service Consultant. After numerous follow ups, I received no feedback. I just saw an email from Avis, with an invoice that states that I owe a certain amount for overdue rental, which does not make sense because the vehicle was returned on time.

This is not the first time experiencing sich a pathetic service from Avis. If it's not charges for pre-existing damages, it's overcharging for rentals and now this??? I have had it with them and demand my refund asap!