Cancelled assignments: compensation

Hello everyone,

This summer, I was going to coordinate six events. Three of them have now taken place and been paid. In the meantime, I noticed that the organiser is mismanaging the business and dismissing other suppliers indiscriminately. And now it’s my turn.
In my previous sales invoices, I included a clause stating that compensation must be paid if the customer breaches the agreement. (Of course, the organiser has not read this yet).

There is no official contract, but there is plenty of email correspondence about my rates and the planning of all events.

What is the best way to to handle this?

Thanks in advance.

JD