Invalid Invoice copy received for mobile phone.

Few days back I ordered smart phone (Lenovo P780) from Flipkart, but when I asked for invoice I got it without IMEI number.

It’s been more than 2 weeks and I am chasing for the valid copy of invoice but I am told that the seller is not responding. There is case registered with Flipkart and incident number is [Incident:140725-021031]

AND most pathetic resolution from FLIPKART,

Since they have given 2 options to me after raising case with their customer care. One is return the product completely and get the refund and another is keep the product without invoice copy along with 10%
Refund amount of the product.

I mean What service FLIPKART is offering??