Monopolistic Toyota!!

A friend got his Toyota Fortuner after one year from booking. He paid Rs. 1,000,00 (USD2200) as the booking amount and was promised 4% annual interest on the booking amount till the time he gets the car. At the time of delivery (after one year), the dealership denied this interest amount even though it was promised in writing. The behaviour of the dealership representing Toyota is totally monopolistic. How can Toyota allow this?