cheated by royal nissan (jaipur) executive are rude after booking car

I have been cheated by the nissan showroom royal nissan jaipur as i had booked nissan sunny and i gave the booking amount rs11000 of which receipt has not given to me. and the nissan executive told me that we will get the car in next twenty days.but unfortunatly i have to cancel my car due to some reasons.and i went after 10 days to showroom to cancel my car . now they are deducting 5000 rs from 11000 and giving me 6000 .it was not told to me that if i cancel the car my 5000 rs wold be deduct from that amount . they dont have any written document snged by me .as this way i have been cheated.