Each transaction must be paid in full with one payment method. The amount of the purchase is shown on the payment pages when entering the billing information.
For example: You can purchase a 12 month Turbo Builders Club membership with your credit card OR you can combine Roblox Game Cards to reach the full purchase price of the 12 month Turbo Builders Club membership. However you can NOT combine Roblox Game Cards and another payment method to make a purchase.
For more information on matters related to billing, including accepted methods of payment, please see the following pages: