I am speaking from experience, so this information is authentic. I know a particular filling station in Ago Palace, Okota, Lagos where the attendants there always cheat their customers.
I learnt it the hard way after they have cheated me more than three times. On the second occasion, I even questioned them, but because I was not sure I let it go.
After my findings, I returned to buy fuel for my car at the same petrol station, at this time my eyes were wide open to see if they will use the same trick on me. Guess what? They did! I shouted at this time and I protested that she should complete my fuel. She did not argue, she reprogrammed the meter to complete the sales.
Now, this is what you need to know when you are buying fuel. After they programmed the amount of fuel you want to buy, fix your eyes on the meter. They will like to distract you by engaging you in a discussion or show you something to fix in your car, don’t allow them.
This is how to know if your fuel is incomplete if after selling the fuel the amount on their meter is blinking, your fuel is not complete. Upon completion of your fuel, the final amount on the meter will be stable or steady, not blinking.
You can also educate someone about this. We must fight corruption from the grassroots, not only at the top.