Bajaj Finance — demanding excessive instalment of loan

Sir, after making a down payment of Rs 12000(against total of 32000) i had taken a loan of 20000 fro the company with the purpose of payment of whole amount of 2500 in 8 instalments . however despite zero interest /charges said by the company as well as the dealer M/s Anil Electr of sarojini nagar New Delhi, not taking other scheme or card from them, much to my surprise i have found the instalment to be 2598/-.which is highhandedness on part of bajajf. i accordingly request for making it correctly as 25000. my reference number is loan 4010CD10231837