Do you mean that the shop sold an item to you for a particular price and then sold the same item to another customer for a different price? If so then I suppose they can if they want to as it is up to them what they charge for all their stock.
doesnt work like that here Ethel prices must be displayed including any discounts . The over 60's dont get discount unless via a voucher from social welfare etc. Students get a discount in some stores but they have a sign in the window. There is certain days its cheaper for over 60 say in salons but that must be specified