PHP - How to access Twilio in a composer namespace environment

I've been working with Rachet WebSockets and created a simple chat application. The example uses a WebSocket namespace. This is my first time using namespace. Now I'm trying to add Twilio service but can seem to add Twilio to my namespace.

I know it is autoloaded in the autoload_files.php

<?php

// autoload_files.php @generated by Composer

$vendorDir = dirname(dirname(__FILE__));
$baseDir = dirname($vendorDir);

return array(
    $vendorDir . '/twilio/sdk/Services/Twilio.php',
);

In the composer.json file

{
    "autoload": {
        "psr-0": {
            "Websocket": "src"
        }
    },
    "require": {
        "cboden/ratchet": "^0.3.3",
        "twilio/sdk": "^4.5"
    }
}

I followed the steps from this website : https://www.twilio.com/docs/libraries/php#using-without-composer

I'm calling twilio inside a method of my class like this:

$AccountSid = "xxxxxxxxxxxxxxxxx";
$AuthToken = "xxxxxxxxxxxxxxxxx";

$client = new Client($sid, $token);

$message = $client->account->messages->create(array( 
    'To' => "+555555555", 
    'From' => "+555555555", 
    'Body' => "This is a test",   
));

Keep getting this error: Uncaught Error: Class 'Websocket\Client' not found in ......

I'm very new to composer and namespace, hope this is enough information to help me.

I had to update Twilio,

ran composer require twilio/sd

- Removing twilio/sdk (4.12.0)
- Installing twilio/sdk (5.4.1)
Downloading: 100%         

Now I'm able to use Twilio\Rest\Client; since it was missing before.