Add Function to Return Message to Branch Head in Complaint Sequence

Description: We aim to implement a new function that will facilitate a more effective communication within our complaint sequence by returning a message to the head of the branch. This function should be capable of accepting several parameters - a gas station number, phone number, and the complaint, and subsequently returning a string with a message.

Acceptance Criteria:

• The function must accept three parameters: gas station number, phone number, and the complaint.
• The function must return a message string that accurately reflects the input parameters.
• The function should handle invalid inputs gracefully and return a helpful error message in such cases.
• The function should be fully unit tested and all tests must pass.

Additional Information:

It would be beneficial to examine other similar functions or services that return messages based on various inputs to get inspiration on how to structure our function and the messages it returns. Ensure to follow our internal coding and testing standards during the implementation.

Estimation:

This task is estimated to require 2-3 days of development time for implementation, testing, and any required debugging. Please note this estimate may vary based on the complexity of the underlying logic, testing requirements, and potential edge cases that may arise during development.