Since the company fired Wang, it should inform the customer. It was precisely because the customer was not informed of the matter that the dispute was caused. Then, the company should explain the situation to the customer, try to terminate the contract or solve it by other appropriate methods. Obviously, this is the reason for putting yourself in the dock on the grounds that "Wang has no right to act as an agent".
Since the defendant went to court, he had to produce evidence to prove that the contract signed by Wang with the customer in the name of the company was invalid, and asked the court not to support the plaintiff's claim. Of course, the company settled with the client firm under the mediation of the court, thus canceling the contract without hurting the harmony.