The Panopticon/Dr.Who or just The Doctor?

I just want to know, if the Doctor was known as 'Dr.Who' in the Classic does it mean all the Classic Doctors officaly called Dr.Who in the episodes castings will have to be changed from "The Doctor" to Dr.Who?. I mean as in casting wise like: The Doctor, Sara Jane,etc. Sorry if I may sound confusing, but I am confused myself. .0.