D-Mart / Avenue Supermarts — Extra Payment charged

I did shopping from DMart Outlet in Indore of worth Rs 2928. However, in one of the product (NIVEA POWERFRUIT) in DMart store was displayed has BUY 1 GET 1 FREE. After reaching home, i saw that i was charged for both the units of NIVEA POWERFRUIT and BUY 1 GET 1 OFFER was not applied in the bill. I tried to reach out to DMart Indore Outlet and they told me that they mistakenly wrote this offer and it was applicable. Now, i purchased this product only because there was offer applicable .