curl --request POST \
  --url https://api.returnshelper.com/uat/user/api/Fba/FbaInstructionReplenish/assignNewFnsku \
  --header 'Content-Type: application/json' \
  --header 'x-rr-apikey: <api-key>' \
  --header 'x-rr-apitoken: <api-key>' \
  --data '
{
  "fbaInstructionId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "assignNewFnskuPayloadList": [
    {
      "oldFnsku": "<string>",
      "newFnsku": "<string>"
    }
  ]
}
'

import requests

url = "https://api.returnshelper.com/uat/user/api/Fba/FbaInstructionReplenish/assignNewFnsku"

payload = {
    "fbaInstructionId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "assignNewFnskuPayloadList": [
        {
            "oldFnsku": "<string>",
            "newFnsku": "<string>"
        }
    ]
}
headers = {
    "x-rr-apikey": "<api-key>",
    "x-rr-apitoken": "<api-key>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {
    'x-rr-apikey': '<api-key>',
    'x-rr-apitoken': '<api-key>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    fbaInstructionId: '3c90c3cc-0d44-4b50-8888-8dd25736052a',
    assignNewFnskuPayloadList: [{oldFnsku: '<string>', newFnsku: '<string>'}]
  })
};

fetch('https://api.returnshelper.com/uat/user/api/Fba/FbaInstructionReplenish/assignNewFnsku', 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://api.returnshelper.com/uat/user/api/Fba/FbaInstructionReplenish/assignNewFnsku",
  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([
    'fbaInstructionId' => '3c90c3cc-0d44-4b50-8888-8dd25736052a',
    'assignNewFnskuPayloadList' => [
        [
                'oldFnsku' => '<string>',
                'newFnsku' => '<string>'
        ]
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "x-rr-apikey: <api-key>",
    "x-rr-apitoken: <api-key>"
  ],
]);

$response = curl_exec($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://api.returnshelper.com/uat/user/api/Fba/FbaInstructionReplenish/assignNewFnsku"

	payload := strings.NewReader("{\n  \"fbaInstructionId\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"assignNewFnskuPayloadList\": [\n    {\n      \"oldFnsku\": \"<string>\",\n      \"newFnsku\": \"<string>\"\n    }\n  ]\n}")

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

	req.Header.Add("x-rr-apikey", "<api-key>")
	req.Header.Add("x-rr-apitoken", "<api-key>")
	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://api.returnshelper.com/uat/user/api/Fba/FbaInstructionReplenish/assignNewFnsku")
  .header("x-rr-apikey", "<api-key>")
  .header("x-rr-apitoken", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"fbaInstructionId\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"assignNewFnskuPayloadList\": [\n    {\n      \"oldFnsku\": \"<string>\",\n      \"newFnsku\": \"<string>\"\n    }\n  ]\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.returnshelper.com/uat/user/api/Fba/FbaInstructionReplenish/assignNewFnsku")

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

request = Net::HTTP::Post.new(url)
request["x-rr-apikey"] = '<api-key>'
request["x-rr-apitoken"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"fbaInstructionId\": \"3c90c3cc-0d44-4b50-8888-8dd25736052a\",\n  \"assignNewFnskuPayloadList\": [\n    {\n      \"oldFnsku\": \"<string>\",\n      \"newFnsku\": \"<string>\"\n    }\n  ]\n}"

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

{
  "data": [
    {
      "fbaInstructionItemId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "apiId": 123,
      "fbaInstructionId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "fbaShipmentItemId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "instructionItemQuantity": 123,
      "fnsku": "<string>",
      "trackingNumber": "<string>",
      "receivedNumber": "<string>",
      "newFnsku": "<string>"
    }
  ]
}

{
  "correlationId": "<string>",
  "meta": {
    "status": 123,
    "data": {},
    "errorCode": "<string>",
    "error": {}
  }
}