Would it be considered rude to suddenly start calling someone by their given name, like, should you ask permission to do so first? if you don't ask permission, and this someone only wishes to be called by their family name, is it seen as though you're mocking them, or intentionally being rude?

edit: i mean, how rude would it be seen as? is it seen as taboo, or just generally greatly frowned upon in society?

edit: I have looked at the posts addressing politeness, but it doesn't answer my question here.