Trident Hyundai — They spoil my rear wiper

Address:

Bangalore, Karnataka, 560071

I had given my Hyundai Santro KA 03 MB 8912 for servicing to Trident Hyundai on Koramangala-Indiranagar Ring Road, Domlur, Bangalore on March 12, 2016. When I took back the car I didn't notice that my rear wiper was up since it was dark. The next morning i couldn't put it down since it was not working. I called them immediately and they promised to repair it. I was out of town for 2 weeks and returned only on April 2. When I took it to them they said the motor is spoilt since somebody forgot to switch it off. I said it wasn't me since it didn't even turn on for me to forget to turn it off! They said they will order the part and since it's an old car they weren't sure how long it will take and that they will call me as soon as it arrives. I went there today and they said they used the part in some other car and will order again for me! Now they are asking me for Rs. 8500 for a part that they broke! This is after they admitted to me that it was working when they got it and that it was not working when I received it! I want my rear wiper to be repaired at no cost to me since it was fine when I gave the car to them.