You're seeing a small amount charged (and then refunded in the form of a credit) from Yahoo! as a test to verify that you are, in fact, who you say you are. We vary the amount of the credit from user to user, and by asking you to provide this exact amount in the verification window of your Yahoo! Voice account page, we can firmly establish that, well, you…are you!

With credit card fraud now affecting millions of people, we've found that this account-check method is an effective way to verify that our users are who they say they are – and not someone else.