"500: Internal Server Error" problem

Whenever I try to purchase the 1-month WoW subscription, the “500: Internal Server Error” keeps showing up. I’ve already tried all the recommended solutions (clearing cache and cookies; disabling any extensions; trying a different internet browser), but it keeps happening. Been at it for more than 3 hours, still no progress. Already submitted a ticket, but it’s taking some time, so I figured I could ask here.

I’m currently going through the exact same issue today.