curl --request POST \
  --url https://scx-sbx.api.jtl-software.com/v1/channel/order/return \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "sellerId": "4711",
  "orderId": "43523-43432-43532",
  "channelReturnId": "R12343",
  "orderItem": [
    {
      "orderItemId": "5437233",
      "quantity": "1.0",
      "note": "<string>"
    }
  ]
}
'

import requests

url = "https://scx-sbx.api.jtl-software.com/v1/channel/order/return"

payload = {
    "sellerId": "4711",
    "orderId": "43523-43432-43532",
    "channelReturnId": "R12343",
    "orderItem": [
        {
            "orderItemId": "5437233",
            "quantity": "1.0",
            "note": "<string>"
        }
    ]
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    sellerId: '4711',
    orderId: '43523-43432-43532',
    channelReturnId: 'R12343',
    orderItem: [{orderItemId: '5437233', quantity: '1.0', note: '<string>'}]
  })
};

fetch('https://scx-sbx.api.jtl-software.com/v1/channel/order/return', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://scx-sbx.api.jtl-software.com/v1/channel/order/return",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'sellerId' => '4711',
    'orderId' => '43523-43432-43532',
    'channelReturnId' => 'R12343',
    'orderItem' => [
        [
                'orderItemId' => '5437233',
                'quantity' => '1.0',
                'note' => '<string>'
        ]
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://scx-sbx.api.jtl-software.com/v1/channel/order/return"

	payload := strings.NewReader("{\n  \"sellerId\": \"4711\",\n  \"orderId\": \"43523-43432-43532\",\n  \"channelReturnId\": \"R12343\",\n  \"orderItem\": [\n    {\n      \"orderItemId\": \"5437233\",\n      \"quantity\": \"1.0\",\n      \"note\": \"<string>\"\n    }\n  ]\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://scx-sbx.api.jtl-software.com/v1/channel/order/return")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"sellerId\": \"4711\",\n  \"orderId\": \"43523-43432-43532\",\n  \"channelReturnId\": \"R12343\",\n  \"orderItem\": [\n    {\n      \"orderItemId\": \"5437233\",\n      \"quantity\": \"1.0\",\n      \"note\": \"<string>\"\n    }\n  ]\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://scx-sbx.api.jtl-software.com/v1/channel/order/return")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"sellerId\": \"4711\",\n  \"orderId\": \"43523-43432-43532\",\n  \"channelReturnId\": \"R12343\",\n  \"orderItem\": [\n    {\n      \"orderItemId\": \"5437233\",\n      \"quantity\": \"1.0\",\n      \"note\": \"<string>\"\n    }\n  ]\n}"

response = http.request(request)
puts response.read_body

{
  "errorList": [
    {
      "code": "GEN500",
      "message": "Internal Server Error",
      "severity": "error",
      "hint": null
    }
  ]
}