Why did I get charged during my free trial period?

Users who activate a free trial via a promo code or other offer may notice a $1 charge on their card. In the past we had people signing up multiple times for our free trial falsifying their names. It hurts our customers and members more than us. We, therefore, instituted this fraud prevention method whereby the credit card company authenticates the individual signing up. They do that by making a $1 transaction that is automatically refunded a few days later.