The project manager should develop an integrated change management plan to control the situation, as this will help to establish a clear and consistent process for managing and approving change requests throughout the project. An integrated change management plan defines the roles and responsibilities of the change control board (CCB), the criteria and procedures for evaluating and approving change requests, the tools and techniques for tracking and reporting change requests, and the impact of change requests on the project baselines and other project documents. By developing an integrated change management plan, the project manager can ensure that the change request process is transparent, efficient, and aligned with the project objectives and stakeholder expectations. Redefining the communications management plan may not be sufficient, as it only addresses the information needs and communication methods of the project stakeholders, but not the change request process itself. Documenting the risk in the project risk register may not be relevant, as the question does not indicate that the change request process poses a risk to the project. Reviewing the scope defined in the project charter may not be helpful, as it only provides a high-level overview of the project scope, but not the details of the change request process. References: PMBOK Guide, 7th edition, pages 123, 124, 125, 126.