How to cancel virtual credit cards

Hello! I am hoping someone may have some advice on how to cancel a virtual credit card when there is no refund option given? Here is the situation:

Our guest reserved and paid for a room through booking.com. However, the engine said we only had double bed smoking rooms available, so that is what he went with even though he really wanted a single non-smoking room. When he showed up we tried changing his reservation to a room he actually wanted, and it wouldn't let either of us do so. So we cancelled his reservation through the booking.com and he paid for the room through Innroad instead (with a different credit card than the one on booking.com). However, the virtual credit card still says there is money on the virtual credit card and the guest says he has a hold on his account. There is no option that says "refund", so I am concerned about what to do. We don't want our guest to pay twice, or to have a hold on his card for a year. 

ANY ADVICE WELCOME! Please send your advice to our hotel email at ***   Thank you!

Kathleen Linder, Riverside Inn employee

Riverside Inn

Thank you! I already sent an email a couple of weeks ago but will attempt to contact again! Thanks again.