Indian Oil Corporation [IOC] — petrol pump issue

Address:

Hyderabad, Telangana, 500039

I work with the central gst and customs department, yesterday i went to the petrol pump located at mehdipatnam, hyderabad the one below the pvnr expressway and asked the person to fill fuel for 500 rs, now this guy fills 100rs first and stops when i told him i asked for 500 he say sorry and now plays the trick to divert me saying card is not working let me check after fuelling and without resetting the nozzle starts to refuel from the same 100 rs untill 400rs shows on the display.
He says first 100 and now 400 is filled which comes to 500. On confronting him that he dint reset to 0 after filling 100 he said it will automatically reset to 0 on stopping the nozzle. I asked him for the receipt from the machine then he says the machine has an issue so can't print but i can give a written receipt for which i denied.
After arguing for 10-15mins he then called me over to the next machine and refuelled for the remaining 100rs.
If he wasn't at fault he would not have called me to fill the remaining amount fuel, kindly take necessary action against them.
How many people are they cheating daily and encashing in the similar manner... Is this money going to the owner or the person filling the fuel??