Cancel API: Cancel a payment (DELETE: /v2/payments/{merchantPaymentId})
Use the Cancel API to cancel the order itself. Use it when the transaction status becomes unknown due to a timeout or other issue during the payment request.
Note: For information about the time limits for cancellations and refunds, see the specifications for each payment service.
If the cancellation time limit has passed, use Refund a payment (refund).
Refund API: Refund a payment (POST: /v2/refunds)
Use the Refund API to issue a refund for an order that has already been accepted.