Was in Lidl at lunch time today. They have large granny smith apples on sale ... big sign saying reduced from 49c to 29c ... I bought 8. I checked receipt before I left the shop and saw that I had been charged 49c each. Spoke to the assistant who went into office, checked the price list and said "the price is going up today". She wanted me to return them for refund. "I told her no you have to give them to me at the price they were advertised. It's the law". She then issued refund for €1.60.
Check, check, check your receipts!