Charged for no delivery, shocking service.

Yesterday I used the Uber Eats phone app to place an order for the very first time. The order arrived missing an item. I told the driver that I won't accept the order because it is incomplete. I immediately contacted Uber Eats via the app and they responded this morning. After explaining the problem numerous times, they respond my saying that I will be reimbursed for the missing item and that the matter is now closed. So, no order was received, though the app states it was delivered, and I will only be partially reimbursed. The service has been absolutely shocking. I cannot understand how the order can be registered as delivered when I did not take any delivery.