On previous refunds for Bitcoin Miners KNC choose to pay back the amount written on the invoice.
If they now choose to do this differently, it looks to me not only as unserious business, but systematic fraud.

Interpreting the law the way the business can choose what to refund, any business could offer a "dream" product. Then wait for payments in other currencies. And some months later, compare the exchange rates and decide which currency to refund - whichever is worth less.