A doctor is not a job title it describes a qualification.

A student coming out of Medicine School and entering into an internship is an intern! S/he has three degrees, BAO, BCh and MB ie Obs and Gyne, Surgery and Medicine. As such, an intern is nothing (poor choice of words, I do apologise) but spends the year training in both medicine or surgery (mainly) afterwhich they attempt to become part of a scheme (SHO)

The scheme is either in Medicine or Surgery, therefore, they now become a Physician or Surgeon (NOT a doctor). (there is other titles like GP that are separate from physician and anaesthetist)

So if you have studied a PhD, then you are entitled to be called 'Doctor' but only by your peers. Whereas, in Medicine/Surgery, people have afforded Medics/Surgeons so much respect over the years they have been called Doctor.

To further highlight my point, a surgeon is technically known as Mr. (dating back to Surgeons and Barbers Guild in the 1700 - 1800's).

Call yourself what you want as long as you have the qualifications