Have you checked your queue? If it still shows your most recently returned game is out, it may be lost in the mail. If it shows a new game has shipped but you haven't received it, could be same problem in reverse. If games are lost in the mail contact customer service through one of the channels DigitalGuy suggested. If they've received your return, but not shipped a new one, make sure you have games in your queue and are signed up for the correct package.