What he said. ^For any questions or problems about payments, please mail to sales@cubecraft.net, they will respond within 48 hours. Did you get a confirmation of the payment in your mailbox? If so, make sure to mail screenshots of it with your mail so you can confirm that you bought the rank. If you bouhgt it you'll get it no matter what, sometimes a payment error happens though and you'll have to send that mail.
Good luck, hope you recieve your rank soon!