If fulfillment has already been "Accepted" for the order, you will need to contact the Supplier to cancel and refund the order.
This is to protect Suppliers from having their orders canceled mid-fulfillment without warning.
If fulfillment hasn't been accepted for the order, you can cancel and refund the customer. Don't know how to correctly process a Carro refund? Please refer to this article.
If you would like more time to review & edit orders before they're routed to your supplier partners, you can switch to Manual or Delayed Auto-Fulfillment.