Guest didn't showed up and we forgot to mark the booking no show.

The property we are running is in one of the furthest region in India and internet here is unpredictable, One booking was confirmed but the clients didn't showed up, as we was new to booking.com, we forget to mark it as no show and our property was closed for winter too. But now we can see a invoice against the same booking. Any help will be appreciable to wave off the invoice.