curl --request POST \
  --url https://openplatform.gateapi.io/payment/open/institution/v1/pay/order/refund \
  --header 'Content-Type: application/json' \
  --header 'X-GatePay-Certificate-ClientId: <x-gatepay-certificate-clientid>' \
  --header 'X-GatePay-Nonce: <x-gatepay-nonce>' \
  --header 'X-GatePay-On-Behalf-Of: <x-gatepay-on-behalf-of>' \
  --header 'X-GatePay-Signature: <x-gatepay-signature>' \
  --header 'X-GatePay-Timestamp: <x-gatepay-timestamp>' \
  --data '
{
  "refundRequestId": "156123911",
  "prepayId": "1647438500687506",
  "refundAmount": "0.8"
}
'

{
  "status": "SUCCESS",
  "code": "000000",
  "data": {
    "refundRequestId": "156123911",
    "prepayId": "1647438500687506",
    "orderAmount": "1.91",
    "refundAmount": "0.8",
    "channelId": ""
  },
  "errorMessage": ""
}