reassigning new user as service request submitter

How do I move reassign a service request submitter to a new userid once an employee leaves the organization? As default Peoplesoft send all email notifications to the original submitter, and the field is locked once the request is submitted. In this stance the user has left the organization, and the new person in the position has limited access to the service request information and no notifications. Is there a way to remove the original submitter's userid and reassign the request to a new user, once the request is submitted and the field is locked?