Am I being charged? Will the free trial auto-charge me?
Yes. Starting the 10-day free trial requires a credit card. When the trial ends, it converts to the plan shown under Renews as on your Subscription page, and your card is charged.
To avoid being charged: go to Settings → Subscription and click Cancel renewal under Trial period, any time before the trial ends. You keep every feature until the trial's last day, then your account moves to the Free plan at no charge.
Changed your mind? Click Undo next to "Renewal cancelled" to turn the renewal back on.
The Trial period section of the Subscription page always shows how many days are left, the plan your trial renews as, and the renewal date.