Account balance error

Today I preordered MWIII. I had $50 on my account from a gift card. When I preordered the game there was some kind of error as my bank was charged the full $74.19 and the $50 from my account has vanished completely. How can I resolve this? I want to keep the game so it's fine they charged me the full amount, but it's not fine that the gift card money just disappeared.