while watching korean drama I have noticed that a person can suddenly be called in a total different way i.e. by nick-name or even that the official name is changed. The interesting fact is that people are okay with the new name, like "Oh, you want to be called by that name? Okay" or then they do not even question it. Eg. A character´s name in Sad Love Story is Suh Joong-jo or something and then suddenly at some point call him cho joong-kyo. As a note, I have no idea how the romanisation of Korean works. Hangul is much easier to use.
Does this happen in real life in Korea or is this just in drama?
Thank you in advance.