AVIS cheating customers for there own errors

I had a rental car from AVIS due to may car being for repairs. Upon return of the rental car, only a week later does AVIS call me to tell me the screen was damaged and that they won't return my deposit and I must pay an excess. I find this disappointing by AVIS, I had returned the car with no damage. I also have pictures as evidence to show that the car had no cracked screen upon return. I had even called at 11am on Wednesday to inform that to collect the car from the BMW repair center, they only collected the car on the Friday afternoon. This was not in a reasonable time, as I gave ample notice for them to collect. They then spent 3 weeks investigating the issue and no one can give me shred of proof to show the cracked screen, all the managers avoid me on the issue. No one cal show me an inspection slip or anything. Yet, i can show all the proof that the car was returned with no issues, yet I'll get a call to settle the payable amount. I will not pay for this, as I have done nothing wrong, and require deposit to be refunded.