Damages on windscreen!!

I travel to Jhb on a monthly basis and always rent a car via Europcar as their service is always good. I also always add additional insurance for the tyre and windscreen. Due to personal reasons this month I was not able to add this. When I picked up my car at Lanseria I was in a hurry, the Consultant that gave the car to me walked around the car and I signed the tablet. Usually they open the picture of all damage on car. I obviously didnt notice any major damages on the car. I used the car the week and returned it to OR Tambo on Friday. When I handed my car to the Consultant he asked for the car papers and I explained that I picked the car up at Lanseria and signed on the tablet. He then asked if I requested drop-off at OR Tambo and I said yes . I then noticed that he rubbed his finger hard no the windscreen and I turned back and asked what he was doing and he said there is damage on the car windscreen and drew a circle on the windscreen. I said, I didnt cause anything, I am returning it as received. He said well they need to check the papers work from Lanseria. I then received an email from Europcar requesting me to complete an incident form for the damage. I DID NOT CAUSE ANY DAMAGE!! I always take out extra insurance, why the 1 month that I couldnt take out extra cover all of a sudden I caused damage which I know I didnt do! I have rep**** on my email twice without any response from Europcar. I am not being treated fairly as I am not receiving my deposit refund or invoice and sitting with debt. I HAVE NOT CAUSED ANY DAMAGE. I need my deposit returned and an invoice to claim back from my employer as I am now out of pocket. I will not use Europcar again, as it cleary shows, as soon as you don't add all the extras (which you can check your records, I do) then you are liable for 'damages'. I am a professional woman with integrity, I will not leave this here.