One extra call can be a sensible service decision. A recurring pattern of unplanned work becomes harder to manage when nobody acknowledges that the agreement has changed.
The goal is not to make every interaction transactional. It is to keep expectations, capacity and price connected to the work actually being delivered.
Make the current agreement understandable
Describe the deliverables, review rounds, response expectations and customer responsibilities in plain language. Explain what happens when a request changes the work.
If the original agreement is unclear, start by clarifying it together. Do not assume that the customer's interpretation is unreasonable simply because it differs from your internal estimate.
Record exceptions without creating a burden
For each meaningful exception, note the request, additional effort, reason and decision. Distinguish a one-time accommodation from a recurring service change.
For illustration, an agency might provide an extra revision because its first draft missed the agreed brief. That is different from adding a new campaign concept after the original work was approved. The record should preserve that distinction.
Offer a workable choice
When a request expands the work, explain the implications and available options. It might replace an existing deliverable, move the deadline or require a separately agreed price.
Avoid presenting new charges after the work is done without the required agreement. Review contract-specific questions with the appropriate adviser; this process exercise does not determine your legal rights.