I don't know about anyone else. But, I never called Dr Ackerly by any name. I suspect that the proper form of address was Dr Ackerly because I don't even remember a first name. However, I still run into this problem. I have been thinking about asking what is the proper way of addressing my new T (masters in social work, licensed clinical social worker). A psychologist/client relationship is strange because he kind a sorta out ranks you. However, it is treated almost like a partnership because only you can do a lot of the actual work. So, I suspect that it might depend on the individual psychologist/therapist.
I think it might be good to have the client actually ask what is appropriate. I mean I am not very good at figuring that out myself and I am studying to become an addiction counselor. It may also depend the theoretical background of the individual therapist. Psychoanalysis/psychodynamic (Sigmund Freud) would probably want to be addressed as Dr. However, I suspect that client-centered therapists might prefer to use a first name. Maybe the therapist might even say "Whatever you are most comfortable with." I could see that. I mean had it come up with Dr Ackerly, I suspect I probably would have just said, Dr Ackerly because most of my teachers were addressed in that fashion. So it may depend on what makes the client most comfortable. Is your character used to addressing people with formal titles or do formal titles intimidate him/her?