You can collect credit card details for bookings of free classes, courses and tours, for example to charge a cancellation fee or a no-show, provided that the payment gateway you are using offers this feature.
1. Go to the Price tab of the class/course/tour and set its price as 0 
2. In the Payment and deposit tab:
- from the Online Payment  scroll down menu, select that you capture credit card details to secure the booking
- In the Cancellation fee section set a fixed cancellation fee