Not a moron by any strech, You should be able to, but there has been a rather rocky relationship between both, and the functionality on both ends in terms of upgrading and other things are shakey at best.
What I would reccomend is taking one of two courses of action
1) Keeping your GC Account linked to Skotos
If you choose to keep your account linked to skotos, you would have to go via the customer support at skotos.net and they should eb able to help you :)
2) Unlinking your account from skotos
I can from my side unlink your GC account from skotos, if you are involved with any other skotos games, it will not efect them, and you would be able to pay via any of our in house payment methods including Credit / Debit cards, paypal, cash etc
Any further questions or comments, feel free to post abck here or PM me directly Belial GC/RT