Hero Bike — Took much money as service charge

Address:

West Medinipur, West Bengal

Today I went to RAJU AUTOMOBILES, Jhargram, Paschim Medinipur, West Bengal,[protected] with my Achiever(WB34A C 4051) for the 2nd Free Servicing. After servicing they claimed Rs. 450/-(Rupees Four hundred Fifty only) and I paid 450 instantly. But they only changed the Engine Oil(Hero 4T-Plus, packed on 04.04.12, MRP Rs. 215/- only), and did general servicing without Washing. They did nothing extra.
They have not given any Bill for the charges. There my Coupon no was 7780 and serial no was 119.
I can't realise why they took so much money. So is it a Free servicing or Cheating with me