Eh? What's the point of publishing a letter on Twitter? If they've got a contract, they should call their law firm and sue. If they don't have a contract, then they should call their law firm.... and sue their law firm instead.
There's 101 disputes in business. That's why we have contracts and courts to adjudicate. There's no point crying on social media.
Reading more than the title and comments helps a lot. You should consider trying it.