Reminds me of a situation many years ago.

A work colleague consistently called me by the wrong name. One day, when totally fed up with this and his attitude, I corrected him. His response "(his boss) said that was my name so he must be right". Short answer from me "no, he's not" before I produced my driving licence to prove my correct name.

It is disrespectful, especially when you're given that name at birth. Just as disrespectful if you've decided to change and advised people accordingly.