Did you sign up with a banking product to use Pay By refund to collect your fees? Thast the only way you can get it automatically from a refund, I dont use it (cost prohibitive), so I have no clue how it works, sorry.
The only way to absolutely, positively ensure that you are collecting the fee is to have the client personally pay you. It's kinda strange that a lot of us still have the clients pay us directly and somehow we are still in business ------------------ go figure.
Ukraine - hang in there