Europcar Inflated my invoice

I hired a car at Europcar, reference ********** 366. I never got my invoice by email within two days as the policy of the company says. Only got it 12 days later after querying it.

I hired the car at 16:30 and returned it at 1600 the following days. Europcar charged me for two days saying I hired the car at 16:00 hours and returned it at 20:00 hours. Honestly! How can anyone make a four hour mistake, and still be in their job? In August I hired a car from Europcar and their service then was beyond reproach. This time around, not sure what happened. I only need them to investigate my case, amend my invoice and refund the overcharge.