If an order hasn't been accepted by your restaurant, the customer will have the option to cancel the order in their Uber Eats app.
If you team has already begun preparing the order, then the customer will need to reach out directly to the Uber Support to cancel their order.
The Uber support agent will then call you to determine if you've begun preparing the food already.
You will always be paid for orders where you prepare the food. Even if the customer cancels, as long as support can verify you made the meal you will still receive a payment for that order on your weekly payment summary.