Cancelled reservations

Hi,

So, I had received a booking about a month ago for 5 nights, with a request for early check-in (almost an entire day prior to their reservation) and since they were staying for a while, I ever so graciously offered them to check-in early free of charge. 

The guest cancelled the reservation today, on the day of check-in FYI the reservation was non refundable and cancellation costs applied. On a side note, the reservation was made without a credit card.

The bookers seem to very much not intend to pay the cancellation costs

My questions are: What can I legally do to make them pay? Is it possible for booking.com to request their credit card details so they can be charged? Am I entitled to request the money through wire transfer?