Scammed at petrol pump

I went today to fill petrol at Indian Oil petrol pump after Kapurbawadi on the service road after crossing Wonder mall. I asked him to fill petrol of Rs.300/-. He filled petrol of Rs. 172/- after which they pretended that there was some problem with the pump so they had to reset and fill another 128/- Rs. But this time the cashier engrossed me in small talk and the attendent pretended like he filled the petrol. When I went ahead I realized that he had scammed me. Did anyone else had any such experience.