Easy Day — offer

Today i went to my local easy day store on anandpur road garhshankar hoshiarpur and they had a offer on 2 ltr drinks the offer said buy one and get one free, our price 83 rupees when i tried to buy one they said it was 83 rupees but they weren't giving me one free
But if i want to buy two it was 160 rupees so i explained to them what the offer said they agreed that i was right so they let me buy only one but i wanted to buy two cases at the offer price which they refused, they are ripping customers off as a nri i know my offers