You can set that some classes/courses are available only for customers who purchased a prepaid package.
1. Go to Settings>Classes, Courses, Events
2. Click on the specific class/course
3. Go to the General tab
4. In the Package only section, select Customers can make a booking only after purchasing a prepaid package.
How can customers book tours that require the purchase of prepaid credits?
When customers click on that tour/activity, they will be asked to sign in the customer area and buy/use their prepaid package