Lenovo — Used PC given instead of New PC

Address:

Gurgaon, Haryana

Hi,

I have bought a new All-in-One PC (Model C240) from your business partner- Sharda Computers & Peripherals Gurgaon on 20th Dec (Friday) late evening that was a gift to my Son's birthday.
During checking the PC at home on Saturday, 21st Dec, we realized that this is not a new machine and has been used earlier. We called up the engineer of Sharda Computers on Saturday and mentioned to him about it. He told that this is not true and may be; we have some illusion.
After going into more depth; we had find evidence of the usage by someone during Nov month.
I called up on Sunday to the owner of Sharda Computers and complained to him. He deny such thing constantly and told that he will send someone to your home on Monday to check and replace the piece. Nobody has turned up as yet till 9 pm (23rd Dec 13).
Now I need your help to file a complaint / case against them.
Thanks