When communities were implemented, they also roped in members of guilds. They’re technically separate, but connected in a few distinct ways.
You’re going to have to reach out to Billing to have this reversed, unfortunately. You can submit a ticket now, or wait until the morning when Live Chat is open, would be my recommendation. It’s generally the expedient way.
At the top of the page, whichever route you choose to go, click Support. Navigate to WoW and then Payments. Find the option Purchase Failure and then go from there. Keep your ticket short and sweet so the reviewing GM doesn’t get confused by muddying information.