Cancellations in the Happity dashboard don't automatically issue a refund, as often a class transfer is more appropriate.
However, if you need to refund a payment, you can do this via Stripe.
Refund a payment in Stripe
i. Log in to your Stripe account at https://stripe.com/
ii. Type the email of your customer into the search bar at the top and press return - this will return a list of transactions from that customer
iii. You can click on the refund payment button from the search results straight away, or click on the transaction to view more info first.
The refund button is at the top right if you click on a payment to view the full details.