It's weird how it works with our petrol, you get told what to sell at and then get forced to change it because of local competition. We try to compete with local stations, within a certain radius, which is why sometimes you get people going "Well it's X at Y petrol station/The Tesco in Z." Plus they made us phone up those petrol stations twice a week to ask their prices.
One dude tried to get about 50p off a litre as he was driving in whilst I was outside changing the price display on the gantry. Naturally he wanted to bitch at a manager who soon backed us up.