Europcar charges for fuel even if you return the car with a full fuel tank.

I am very disappointed with the services. They think people do not check their invoices after rentals so they charge for things that don't exist. I rented a car (Agreement number : ***) on the 30th of November for only 2 days. Upon the return of the car, I went to the Engen that is nearest to the branch to fill up until it was full. Drove like 2-3 blocks then dropped the car. When my refund came, i was shocked because suspected i was overcharged as i only expected etolls charges only. Upon querying i was informed that 15L was refueled into the car. Which is totally a mistake because when i dropped the car it was full. Nobody from Europcar has contacted me to resolve this issue and i have been waiting. Can someone please look into my query - query number 550095. Thank you.