DIESEL PRICING - FUEL DISCOUNTS

Mad Dog may be able to answer this one as it concerns the area in which he lives.
Last year a second supermarket chain got into the act by taking over the fuel outlets of a large fuel company, beginning in the southern states.
In a certain city near Melbourne through which I regularly pass, the new fuel outlets no longer post diesel prices on the board as the fuel company used to. They post unleaded and LPG prices which are usually the same as their competitors. I have looked over the past five weeks at their diesel pricing policy, and guess what. It is always 6 - 8 cents higher than competitors just down the road who display diesel pricing, makes a mockery of the 4 cent discount thing.I have questioned pump jockeys at the four outlets concerned and all gave me a 1800 customer service number to call, which I have, only to be given the "market forces - it's what we buy it for" type line. Problem is the same brand outlets in smaller towns around this one all display diesel pricing - at the lower price of the competitor outlets in the city. To my way of thinking it is simply a dishonest pricing structure which will catch out 90% of people after it is too late. I was one of the 90% who got caught the first time, had $50 worth in the tank before I noticed the price, (the price only appears once you lift the nozzle). What is the next step??????
Rolande