Big Bazaar / Futurebazaar / Future Retail / Hometown — price related

Address:

Simli pandriva sakha gali opp Devi asthan Sudama sewa sadan po. madhavmills ps. Malsalami, Patna, Bihar, 800008

Hello, i purchased in 22/01/2020 sabse saste din a pack of turmeric powder, chili powder, coriander powder in offer buy 2get 1 but price of half kg turmeric powder is 130 and price of 1kg is 160 why big bazaar making fool. I want to exchange but there is no any option for exchange then what i do. There is lot's of difference between half kg price and 1kg price but i there is only only difference of 30rs. I want to exchange this.