Opinions please.

A venue we supply has cancelled 6 bookings in December. These are all contracted bookings and 3 are on Saturdays. Even though the bookings were confirmed, signed and contracted, they dont want to pay the cancellation fees involved and have made a thinly veiled threat that if I do charge, they might be looking elsewhere in the future.

I have tried to be flexible and not charge for 3 of them and this is a decent venue that does give me quite a lot of work. I feel it makes a mockery of my contracts which is suppose to protect both parties.