I would define being professional on the phone as the general "doing unto others" principle. I would say being professional is pretending they are sitting there with you and can see your nonverbal communication.
For example:
1. Actively listening and pretending I am looking at the individual in the eyes. Not
working on my computer or doing other things.
2. Trying to reciprocate my communication style to be similar to theirs. (I.E. the age and terms used by an individual).
3. Walking a little while in their shoes as they share their history. Meaning being proactively empathetic to specific life events that have brought to me as a student.
4. Anticipating the students needs based upon what they are telling me in their history.
5. Saying their name and making it personal, while always using basic manners. Please, thank you.. etc.