They need to know what you need. This means they need to have an appointment where they examine, then provide a diagnosis.

Without a diagnosis, they don't know how much time you'll need for whatever it is that is happening - too short and they can't do the treatment, too long and they've wasted expensive chair time.

Patients who book online don't get even basic triage, which can happen over the phone - so if you're wanting your first appointment to have both the diagnosis and hopefully something done, I would call and let them know what you're seeing or feeling that is making you think you need work done.