The announcement of Battle for Azeroth pre-purchase and unlocked Allied Races playable immediately triggered an avalanche en masse of players attempting to pre-purchase. This caused the third-party server to get overwhelmed, and the order wouldn’t get through giving a generic error.
The problem is that each attempt to complete the order listed multiple charges to your credit card that are now sitting there as Pending Transactions.
My credit card provider contacted me within an hour to investigate why there were multiple charges from Blizzard Entertainment. I explained the situation, and they suggested to reach Blizzard Customer Service.
When I tried to reach them via Online Chat, this is the automated message provided by Blizzard: