It's not clear what made you think that TurboTax is free. Most versions of TurboTax are not free. Only TurboTax Free Edition is free. The tag below your question indicates that you are using TurboTax Deluxe, which is not free.
If you started in Free Edition, and you are now in Deluxe, then you must have accepted an upgrade. The screen for the upgrade told you how much it would cost before you accepted it.
The other possibility is that you started in Deluxe, and clicked a button that said "Start for free, Pay only when you file." You might have focused on the "Start for free" part, and thought that meant that you would never have to pay.
