How can I refund a payment without an associated order number?

[danspark]

We have a customer paying twice a draft order, which resulted in 2 payments visible only in Payouts without associated order numbers.

Customer demands a refund of one of the payments, however there is no way in the system to do this, because there is no associated order.

Shopify customer service is useless, their escalations team has not replied for 24 hours.

Will appreciate any advice?