Individuals have the right to have personal data rectified if it is inaccurate or completed if it is incomplete.
An individual can make a request for rectification verbally or in writing.
You should respond to a request without delay and at least within one month of receipt.
You should calculate the time limit from the day after you receive the request (whether the day after is a working day or not) until the corresponding calendar date in the next month.
You can download a description of individuals’ rights under GDPR here