The job: get the right patient back at the right time
A recall scheduler answers a narrow question every morning: who is due to come back today, and has anyone told them. Everything else in the workflow exists to make that list correct, contactable and honest about what has already been tried.
How it is done today
The classic version is a recall diary. At the end of a visit the receptionist writes the patient's name on a page dated six months ahead. It works surprisingly well until a page is missed, a receptionist changes, or the patient moves the appointment, at which point the entry exists in a past date and is never seen again.
The other common version is a spreadsheet with a due date column and a filter. Better, because overdue entries stay visible. It still cannot send the message, so contact happens from a personal phone and the attempt is recorded only if someone remembers to go back and type it.