I use my first name with everyone I call by their first name. People who prefer to be addressed by their last names address me the same way. Simple enough

(In front of patients I always use the other person's title).
Maybe my parents were just old fashioned, but that's how I was raised. I address people how they want to be addressed and expect them to address me with the same level of formality. Someone calling my by my first name if they insist on being called by their last name is disrespectful IMO. Children and pets are the only living things without last names. I'm neither.