10% ICICI bank debit card instant discount offer not getting applied on purchase of mobile phone with exchange on Flipkart

I was trying to buy a mobile phone on Flipkart with exchange and the 10% instant debit card discount (up to ₹500 for minimum net cart value of ₹5000 & above) is not getting applied. But when I try to buy the same phone (or different phones) without exchange the discount gets auto-applied. I tried to check if this is happening with just one phone or different phones so I tried it with different phones WITH exchange & the discount never got applied. Read their Terms & Conditions which clearly said that the offer is applicable if the Net Cart Value after all applicable discounts & "Exchange offer redemptions" is more than ₹5000. So it seems there's a glitch in their system and the offer is not getting applied if one tries to purchase a phone with exchange. The customer service wasn't helpful either and their response was that maybe your debit card is not eligible which is rubbish as the offer gets applied if I try to buy any phone without exchange. 

Is anyone else facing the same issue?

Check Points 6 and 12 of Terms and conditions