I wish I had better news, Jowus, but Monday is probably the busiest day of the week. Also, those of us here on the Customer Service Forum address in-game issues and topics that pertain to the Game Master department - Billing & Account Services are an entirely different department that we are unable to assist with. Hopefully you aren't waiting too much longer.
I really couldn't say for certain when the best time to call would be, but I can tell you that on Mondays after having been closed for the weekend is going to be a very busy time to call.