Those of you experiencing this issue should be able to re-enter your method of payment by going to the status page for Race Changes. It looks like payment has not fully pended, and needs to be re-entered to continue.
Race Change Status Page https://www.worldofwarcraft.com/account/race-change-transactions.html
Looks like there may be something more to this. Going to have some of our talented billing guys take a glance. As soon as I'm able to provide an update, I shall. >^.^<