I want to take CCD to Consumer Court

I went to the Cafe Coffee Day Lounge in Hauz Khas. It is nice with a relaxed atmosphere.
But then ... [there's always a but!] today I ordered a cappuccino. [Do you remember this blog started because of a cappuccino/cafe latte mess up at the same CCD.] And ok, I got one. When I got the bill they had charged me for Big Grande! Now what the hell is a Big Grande? I asked. He said it is a big Cappuccino. I said I asked for a regular one. He said "we did not have it, so we served Big Grande." And they charged me more for that. Ok, the price difference was just Rs. 5, but I felt cheated. So I said, I will pay. But please write in the bill that a cappuccino was ordered and that they served big grande because they did not have a cup in which they serve cappuccino.
The guy apologized! He said it was their mistake and charged me Rs. 50 which is the cappuccino price.

But how many of us check the bill. The total in my bill was Rs. 136 and I do not think a Rs. 5 difference makes much of a difference to anyone.

Ever since I moved back from US, I am hearing a lot about this consumer court. I thought I would take them there. But I do not have any proof that I ordered cappuccino and got Cafe Grande! Any suggestions?

India is so much a seller's market. They rule!