public function GetAttachment($MessageGroupID, $MessageUid, $ContentKey = "image-data-0", $ContentType = "image/jpeg")
{
    $headers = array(
        'Authorization: Bearer ' . $this->oauth,
        'Content-Type: ' . $ContentType,
        'Content-Transfer-Encoding: binary'
    );
    $response = \Utilities::SendRequest(MESSAGE_URL . '/' . $MessageGroupID . '/messages/' . $MessageUid . '?contentKey=' . $ContentKey, $headers, false, null, "GET", null);


    $data = base64_encode($response['body']);

    return $data;
}

// Get Audio
if (!file_exists($FullAudio))
{
    $AudioData = base64_decode($MessageAPI->GetAttachment($MessageGroupID, $Messages->messages[$i]->messageUid, "voice-data-0", "audio/mpeg"));
    $fp = fopen($FullAudio, 'x');
    fwrite($fp, $AudioData);
    fclose($fp);
}

// Set Path to Audio
$Audio = '<audio controls>';
    $Audio .= '<source src="/psn/audio/' . $FullAudioName . '" type="audio/mpeg">';
    $Audio .= 'Your browser does not support the audio tag.';
$Audio .= '</audio>';
$Content .= $Audio;