Small business owner here...I use Wave for accounting. They absolutely do refund the fee. Shame on the processors who don't refund it, and shame on those who hasn't been doing that since the beginning (Strip, Paypal...) because they are knowingly sticking it to small business owners. I've used Wave for 4.5+ years and this is how I've known it.

"Regardless of the type of payment you received, the full amount that the client paid will be refunded to the client by clicking on the refund button at the bottom right-hand corner of the transaction details."

https://support.waveapps.com/hc/en-us/articles/115004056523-...