var unirest = require('unirest');
var unirest = require('unirest');
var accountSid = "XXXXXXXXX";
var accountToken = "YYYYYYYYY";
var authKey = "ZZZZZZZZZZ";

var encoding = Buffer.from(authKey + ':' + accountToken).toString('base64');
var req = unirest('PUT', 'https://<subdomain>/v2/accounts/exotel8u3/contacts/<contact_sid>')
  .headers({
      Authorization: 'Basic ' + encoding,
      'Content-Type': 'application/json'
  })
  .send(JSON.stringify({"first_name":"XYZ"})
  .end(function (res) { 
    if (res.error) throw new Error(res.error); 
    console.log(res.raw_body);
  });

<?php

$curl = curl_init();
$accountSid = "XXXXXXXXXX";
$accountToken = "YYYYYYYYYY";
$authKey = "ZZZZZZZZZZ";

$encoding = base64_encode($authKey .":". $accountToken);
$curl = curl_init();

curl_setopt_array($curl, array(
  CURLOPT_URL => 'https://<subdomain>/v2/accounts/exotel8u3/contacts/<contact_sid>',
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => '',
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 0,
  CURLOPT_FOLLOWLOCATION => true,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => 'PUT',
  CURLOPT_POSTFIELDS =>'{
            "first_name": "captain"
}',
  CURLOPT_HTTPHEADER => array(
    'Content-Type: application/json',
    "Authorization: Basic ".$encoding
  ),
));

$response = curl_exec($curl);

curl_close($curl);
echo $response;

import requests
import base64 
import json
accountSid = "XXXXXXXXX"
authToken = "YYYYYYYYY"
authKey = "ZZZZZZZZZZ"

encoding = base64.b64encode(authKey + ":" + authToken)

url = "https://<subdomain>/v2/accounts/exotel8u3/contacts/<contact_sid>"

payload = json.dumps(
        {
            "first_name": "captain"
        }
        )
headers = {
  'Content-Type': 'application/json',
  'Authorization': "Basic " + encoding
}

response = requests.request("PUT", url, headers=headers, data=payload)

print(response.text)

package main

import (
	b64 "encoding/base64"
	"fmt"
	"io/ioutil"
	"net/http"
	"strings"
)

func main() {
	// Please provide accountSid, authToken from your Exotel account
	accountSid := "XXXXXXXXX"
	authToken := "YYYYYYYY"
	authKey := "ZZZZZZZZZZ"

	// Encoding the accountSid and authToken, used in Authorization header
	encoding := b64.StdEncoding.EncodeToString([]byte(authKey + ":" + authToken))

	url := "https://<subdomain>/v2/accounts/" + accountSid + "/contacts/<contact_sid>"
	method := "PUT"

	payload := strings.NewReader(`{
			  "first_name": "captain"
		  }`)

	client := &http.Client{}
	req, err := http.NewRequest(method, url, payload)

	if err != nil {
		fmt.Println(err)
		return
	}
	req.Header.Add("Content-Type", "application/json")
	req.Header.Add("Authorization", "Basic "+encoding)

	res, err := client.Do(req)
	if err != nil {
		fmt.Println(err)
		return
	}
	defer res.Body.Close()

	body, err := ioutil.ReadAll(res.Body)
	if err != nil {
		fmt.Println(err)
		return
	}
	fmt.Println(string(body))
}