Reddit India had this photo posted by an eagle eyed user with a note that even Flipkart uses Amazon’s own services :

 Flipkart using Amazon's package

Then Reddit India cheekily tweeted this. To this, Flipkart responded in a way you wouldn’t expect :

Flipkart tweet about amazon

Something tells me we have not seen the end of this yet, more so because Flipkart still has not explained from what they got delivered to them.

Amazon Response

Modified to include Amazon’s response above.