This doesn't look like a "account ban", hun. I think your subject is a bit misleading. It's probably a billing issue of some sort -- even if your credit card "went through" initially, the actual amount doesn't get deducted from your card immediately so something could have happened during the processing time. Alternately, it could be some sort of anti-goldspammer precaution that blizzard is doing. Who knows.

Greetings,

This notice is being sent to inform you that we are unable to successfully process the recently requested electronic upgrade for World of Warcraft account <name removed>. As such, this account will remain at the current account level and no charges have been processed for this upgrade. In addition, in order to protect the security of both this World of Warcraft account and your payment method we have disabled access to this account to prevent potential abuse. Please contact the Blizzard Billing and Account Services department via telephone at (800)-59-BLIZZ (1-800-592-5499). Please note that due to security concerns we will be unable to assist you via email.

We apologize for the inconvenience this may cause and thank you for your patience in this matter.

Regards,

Blizzard Entertainment
www.WorldOfWarcraft.com
In any case, if you had any account action (including a ban, suspension, warning) it would clearly say that it was an account action and what the account action was for. This one just sounds like an "oops, we couldn't process your request. Please call us to try again".

Best of luck getting it sorted out!