Dell India — cash back

Hello dell, i purchased a computer on dell website this nov19. While paying there was a offer from paytm on dell website which says, get rs.1000 cash back. It's been almost 19 days, still i didn't get my cash back. I called paytm, they told me the offer is from dell, so i have to call dell. To my surprise dell customer care doesn't know the offer exist. They asked me to call compuindia. Compuindia said they don't deal with offers.
Why do a company like dell do not take things responsibly.
Now i feel i should have purchased through amazon or flipkart.