Fabindia - Fabindia exchange of the item

On ** March **** ,**:**

I have purchased a casual pant from fabindia ,Jamnagar (Gujarat).
I have purchased it on offer.
I paid for it by cash
Bill No : TXBPg***********
Cashier: **E*****

But when it is not go well with.
I get back to there for exchanging but they refused to exchange . They told me that discounted item can't be exchanged. They should told me such a rare policy before but they didn't, not even while making payments.

All other brand like bibo, metro, mochi provide the facilities to exchange the discounted item.
And I have also emailed the customer care of fabindia they are also saying the same thing.