Getting help with a diary clash!

I merge diaries from booking services with Smoobu.

After cancelling a booking from Expedia a Booking.com guest requested a change of dates to the previously cancelled Expedia booking but booking.com won't allow because it perceives a clash.

I have now moved the booking in Smoobu but booking.com has the wrong dates still. Is there a way to override a faulty clash? or someone at booking.com I can contact who can manually correct a fault?