Indian Oil Corporation [IOC] — Filled more than we asked for

Address:

Devaraj enterprise, green glen layout, bellandur, bangalore

I had gone to Indian oil petrol pump devaraj enterprises, Green glen layout, Bellandur, Bengaluru this morning at about 7am. I asked the attendent to fill my tank for 500 petrol. He put the nozzle in and didn't pay attention, when I looked at the meter it was 2570. I had to bang my door to get his attention and asked him to stop. He got the manager and two men came out of the office. One of them (Dhanapal) walked to my car and asked if I was going to pay by card or cash. I told him about the problem and he apologized but still asked me to pay. He said it was the attendant's first day at work so he made a mistake. Then he started calling me a cheapskate for not paying up and leaving. I asked him to pump it out as I had asked him to fill for only 500. So some 10 minutes of explaining, he got angry and walked away. We had to pay 2570. I have heard about this scam before too and don't really know if this is a regular practice there. But why should I have to pay for someone else's mistake. If the attendant was not trained enough then why was he allowed to handle customers? I wonder what they would do on a busy day.!!
Please help.