What you can do if the client has reneged an agreement or commitement and nothing was on paper nor formally communicated on this?

written a note in your lessons learned there in no oral contract ....then start a Negotiation with Clint to reduce the losses

Whilst a contract can be oral, it must be evidenced in writing, If only one party "gives" something, there is only a promise (which cannot be enforced), there was NO contract between you and the client.

management means that you are control all items in project and care to work smoothly, that situation my friend faced before, every word should be writing formally in approved papers or minutes of meeting, this is management tools to control project.