HTC India — Regarding repair of warranty

Address:	Ajmer, Rajasthan, 305001
Website:	www.htc.com/in/support

I have htc d 620 g (purchased on feb 2015), due to flickering display problem (display good at starting but off after short duration), no physical damage or no other problem i send it to jaipur service center via authorized collection point at ajmer and after diagnose they send me a customer unit status (consumed motherboard and diplay unit) and they made a bill of replacing of items cost around 12000. i can't afford i am a student and its also really absurd. then after this i have doubt that may be my original parts replaced with faulted one. regarding this i complained several times but no one paid any heed. i have no idea what to do.
Please help me out regarding this. i will be very thankful to you.