I tried to register/transfer a domain, and it didn't go through, but it looks like I was charged.

all killer.  no filler.

When you make a purchase using a credit card, we “authorize” funds on your credit card. This is not a charge, but a test to make sure you have the funds available for the purchase. After the authorization returns a result of sufficient funds, we register the domains. If the domain registration fails for any reason, the attempted charge is voided. The net result is that your account not charged. In most cases, the original authorization charge is removed from your credit card account within a few days. You can contact your credit provider to find out their specific authorization policy.

If you are having trouble registering a domain, we recommend that you contact technical support rather than resubmitting the order. If you continue to try to submit your order, you will incur a large number of authorizations, and consequently, you may run out of available credit or freeze your account funds. You may even cause your credit card company to suspect fraud, and they will put a hold on your card.