Zero confidence for trustworthiness

Received a car from the CPT airport branch. Arrival inspections showed various damages. Used the car for two days, zero incidents, parked in a secure parking so not even another car door could be mistakenly opened onto the car. Returned the car, no issues, they were too busy to see to our rental immediately, so they said we could leave the keys and they would handle the finalization. This is standard practice and we've had no issues with the car, so no problem right? Received a notice of a claim for a front door dent after use. Incoming inspection shows a front door dent which was already there. Unable to reach them, unable to get a return inspection or photos, just told to fill in the incident form to finalize then rental. Have been phoning non-stop for 5 days now already. No replies to emails, no answers and always being relayed to reception, who doesn't answer. I just want to see the dent and the final report? Because an additional dent without my knowledge is physically impossible. How can you expect clients to just fill in incident reports when you've provided no final inspection report or photo or even description of the vehicle. And now my deposit is on hold but you are unreachable?