Hi Marinas Edge,
All refunds have to be "linked" to a previous payments. That's not our rule, that's a rule that the processing banks establish. In order to do "unlinked" refunds, you have to be credit checked for a different system. That's why our refund screen requires that you select a payment to link the refund too.
That being said, refunds should work on expired cards. Did you try processing the refund to the person's account? Even if the card number expired, the refund SHOULD still go through and wind up back in the person's bank account. That's usually the way it works.
Failing that, the only way to return money would be via a different form such as check or money order.