curl --request POST \
  --url https://public-api.kiwify.com/v1/sales/{id}/refund \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --header 'x-kiwify-account-id: <api-key>' \
  --data '
{
  "pixKey": "99999999999"
}
'

{
  "refunded": "true"
}