Alright, so, this happens pretty much every time I buy premium.
I have a $50.00 pre-paid Mastercard(the same kind I use every time), and the site continues to decline it. I checked with the card manufacturer, it is valid.
As I said, this happens nearly every time(including the time I bought premium for Planks). I would use the contact e-mail provided, but I figure that if I post here instead of my usual PM to an admin, it might result in a permanent fix for this problem.
I will PM an admin with the information for the card later if that ends up being necessary.