Unprofessional from your staff

I have rented 2 Cars for more than a week, everything was fine until I return the cars on Tuesday the 28 I was told that I will receive invoice before they refund my deposit indeed they did sent invoice but only for 1 I have asked for second car but it looks like they have lost the recording of movement of the but my worry is how could you not trace the movement of the car but you managed to charge extra money without invoice of it? It don't make sense at all. I have called in the morning to ask for my invoice just to be told they don't see it