Do banks charge anything from shopkeepers for giving them credit card facility?

Some shopkeepers like jewelers, in electronics shops, charge additional 2% over the price of the commodity if we pay thru credit card and the reason told is that they are charged by banks for this.Is this true or are they fooling the customers? Yesterday I bought a mobile phone and paid by credit card & the same happened to me.Have I been fooled?If yes, what action can I take against this?