petrol price not yet change

On the morning of 05/08/2015 I have filled my vehicle fuel tank at BP Twins Palms Arcadia and only realized that the fuel station has not adjusted the fuel price at 0H00 that evening. When I contacted them during that morning I was told that the card banking machine was not adjusted but the petrol price on the pump was decreased from R13-52 to R13-01, The slip received from the fuel station the previous week proof that the price did not came down as prescribed by the government. I should have paid R15-09 less on the total amount.