ரிலாயந்ஸ் ஹ்ய்பெர்மர்த் லிமிடெட்

I have made purchase from Reliance Retail on 20th Dec-2015. Suddenly check the bill where they charged Amul Butter - 100 G.M @ 40/. INR and in actual MRP was 38/. INR. My bill total was 1276.57 INR. I was shopping from Reliance mall from last 8-9 years and I had never checked the bill. How can they charge more than MRP. Its not a small thing. I am planning to take the help of Consumer Court. I have original bill and amul butter wrapper safely. I have made shopping from Reliance in 9 years approx in how mucjh lakhs no idea. If they charged more than MRP in other bills also then I am and other consumer are also in loss.