curl --request POST \
  --url https://staging-api.getpartna.com/v4/convert/preorder \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --header 'x-api-user: <api-key>' \
  --data '
{
  "accountName": "",
  "fromAmount": 0,
  "rateKey": "",
  "transactionReference": ""
}
'

{
  "data": {
    "transactionReference": "bbcdef2234567890abcdef1234568491"
  },
  "message": "success"
}