Liquor sold above MRP - 1

A couple or so weeks ago I bought many bottles of liquor from Spencers Retail in Koramangla. All the prices charged were above MRP. There were 3 excise department notices that some brands of beer have been increased in price from such an such date (TBD). However, there was no notice for the 6 or 7 different alcohol brands I was purchasing. I called for the manager, spoke to him, explained to him the problems.

1. The purchase price of fresh stock of liquor might have gone up, but that does not mean the old stock was purchased at the higher price.
2. MRP on liquor was made mandatory from (AFAIK) Nov 06. That means the MRP is the final price on that old stock and all taxes have been paid already, and as far as MRP rules go, the price cannot be changed on old stock.
3. Excise duty in India is different from sales tax / service tax / VAT. Its a point of origin or manufacture duty, hence this duty is already charged, whether the sale is made or not. (I need to check into the legaclity of Excise duty increase after the MRP has been printed on the bottle.)
4. Notice was not published for the brands I was purchasing.

He in turn called up his manager, they brought their files for inspection and showed me that the price that they had purchased the beer brand that I'd bought was higher than the MRP printed. And the price that they were selling at was higher than their purchase price, which is of course valid. So I asked for a letter from them stating that they were selling the liquor above MRP and there was no notice. He of course refused.

I purchased all the liquor and took a bill. That makes my posistion secure. Now to find out whether I am in the right, and if so how to nail these buggers.