A customer calls the project manager concerned that a team member made unapproved changes in the live environment, claiming the customer requested them. What should the project manager do next?

The project manager's primary responsibility is to maintain project control and adhere to established processes. Reinforcing the need for documented and approved change requests and directing the customer to use agreed channels (D) addresses the immediate issue by ensuring proper procedure is followed, preventing future unauthorized changes, and protecting the project's scope and integrity. Organizing a mediation meeting (A) is premature; the immediate focus is process adherence, not conflict resolution. Telling the customer the team member was "trying to help" (B) undermines project governance and condones unauthorized actions. Asking the customer to send all requests by email to the PM (C) centralizes communication but doesn't fully address the need for formal change control and approval, which is crucial for project success.