Using Stripe APIs you could set that up. I’m not familiar with the plugin capabilities but you would want to create a payment_intent (Stripe terminology) when they sign up for the session and then use the APIs to collect payment using that payment_intent after the session has been completed.
I would push you to think about that setup though as your intention would make it so that a Seller who is scheduling their time to attend the session will not receive money for a session that a user who scheduled doesn’t show up for, which means just wasted time/money for the seller.
In my Skillup Template which allows Sellers to setup their availability schedules and accept bookings for online meetings through Stripe I take payment at the time of booking and only after successful payment is the booking confirmed. Then both users have the functions necessary to allow them to cancel the meeting and the booker can actually modify the date/time after initial confirmation.
All of that takes place with different ‘Cancellation Policies’ in mind so that if the cancellation policy set by the Seller has caused the time to pass for free cancellation/rescheduling then the Booker will be informed when attempting to reschedule or cancel they will have to pay the cancellation/rescheduling fees.
A setup like that makes it so that there is real value to a Seller to use the platform, rather than potentially causing the Seller to lose their valuable time for bookers who just don’t show up to a scheduled booking.
If you are interested in learning more about how to integrate Stripe through APIs I recently launched a Stripe Integration Course that will teach how to setup your app to utilize Stripe API so you have complete control over the functions and are not limited to the plugin functions.