The related invoiced charge has not been reversed and Stax Bill is collecting on the currently unpaid charge.
Stax Bill separates invoiced charges from payments. As such, refunds are separated from reversed charges. This is so that credits can be issued to customers and applied to future invoices. If the intention is to return the funds to your customer, the charge must first be reversed so that the system will make no further attempts to collect that charge. This approach gives our clients more flexibility and control.