Air BNB waives fees if the cancellation is within 48 hours of booking for most reservations. Here is a link to the Help Center article about refunds including Air BNB fees.
https://www.airbnb.com/help/article/311/find-your-refund-amount
You can refund your fees due to a cancellation, but if the guest cancels, do not refund until the guest goes through the Air BNB process for guest cancellation. If you try to manage it yourself, you might cause there to be duplicate refunds and you will lose future payments.