HTC — Htc desire 826 screen turn off suddenly

Address:	Bangalore, Karnataka, 560066
Website:	htc.com

I bought HTC 820 recently and the phone screen suddenly turns blank.I can't see anything for minutes or hrs then once i use buttons for reboot suddenly the screen is back.I am not understanding how to resolve this issue. i have asked bangalore customer care, they said to replace entire motherboard and they are asking money for their service and replacement . so i have no other option to sell this mobile instead of spending lot of money on repair. Kindly help me