A title can remain on a door after the person has ceased believing it describes them.

A title can persist after the belief in it has gone. The door still says it, the emails still assume it, and the person inside has quietly stopped identifying with the description. There is no procedure for that, so it goes unannounced, sometimes for years, while everything external continues as before.

If you are in that position, ask what you would call yourself if the title were not there. The answer usually indicates where to go next. And it is worth noticing how much of the reluctance to change is about the title itself rather than the work.