Class 'Twilio\Rest\Client' not found error when Client is instantiated - php

Question

I'm trying to integrate Twilio into my application. When I run their sample code, it runs perfectly fine:
require_once "twilio-php-master/Twilio/autoload.php";
use Twilio\Rest\Client;
$AccountSid = "XXXXXX";
$AuthToken = "XXXXXX";
$client = new Client($AccountSid, $AuthToken);
$sms = $client->account->messages->create(
"[phone]",
array(
'from' => "[phone]",
'body' => "Hey, Monkey Party at 6PM. Bring Bananas!"
)
);
However, when I try to integrate it into a class, I keep getting a PHP Fatal Error Class 'Twilio\Rest\Client' not found every time it executes. This is the code in my class:
require_once "twilio-php-master/Twilio/autoload.php";
use Twilio\Rest\Client;
class Customer{
//constructors etc
public function sendText(){
$AccountSid = "XXXXXX";
$AuthToken = "XXXXXX";
$client = new Client($AccountSid, $AuthToken);
$sms = $client->account->messages->create(
'[phone]',
array(
'from' => "[phone]",
'body' => "Hey, Monkey Party at 6PM. Bring Bananas!"
)
);
}
}
I've checked the opening tags in the Twilio Library, I've ensured that the file location is correct (it throws the error when the
$client = new Client($AccountSid, $AuthToken);
line is executed, not at the require_once) but I can't seem to figure out what's going wrong.