PDO class not found in namespace other than global

I am creating a class that uses PDO, but in a namespace other than global:

namespace Classes\Config;

use \PDO;

class Connection {
    public static function getConnection() {
        $dbhost = "algumhost";
        $dbuser = "algumuser";
        $dbpass = "algumasenha";
        $dbname = "algumabase";
        $dbms = "algumsgbd";
        $dbport = "9999";
        $dsn = "$dbms:host=$dbhost;port=$dbport;dbname=$dbname;user=$dbuser;password=$dbpass";
        try {
            $dblink = new PDO ( $dsn );
            $dblink->setAttribute ( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
        } catch ( PDOException $e ) {
            echo 'Erro na conexão: ' . $e->getMessage();
        }

        return $dblink;
    }
}

After trying to use the getConnecton method, I get this error:

Fatal error: Class 'Classes\PDO' not found in path/para/meuarquivo.php on line 69

Does anyone know what I might be doing wrong? Thanks in advance.

Q: I use the composer to autoload my project.

PDP information in phpinfo ():