I have a marvelous Tesco tale.
Bought Mrs Rk11 a Marie Claire magazine which was priced at £2, reduced from £3 odd. Anyway, I also did a big shop and bought 3 glaze candles as they were buy one, get two free @ £4. Paid for it all and realised they’d over charged me by 80p for the magazine and i’d paid for all 3 candles. Quick complaint, they gave me my money back and doubled it so a £50 shop actually cost under £20 in the end.