Flipkart — Misinterpreting marketing strategy thru their website

Hi,
I ordered a phone from Flipkart along with exchange of my older phone. They have clear cut guidelines on their site of what qualifies for reduction in exchange value or denial of exchange. I was incorrectly denied exchange and they mentioned it is upto the delivery boy. This is nowhere mentioned on their site. Moreover to bypass system checks the delivery boy entered incorrect reason “Product Mismatch” in order to deny the exchange. I had called the Helpdesk at that point in time but they couldn’t help. This is misinterpretion of facts and thus I want to file a formal complaint. I tried talking to their senior team members but they put blame on seller and the hang up the phone. This is serious issue.