Business process:

The new adjusted system will make it easier and more faster for the patients to book their appointment without having to wait for a long and inflexible process :

Log in$/$ register: Allows new patients to create an account and login in the system

view the available doctors: Allows patients to view a list of available doctors.

view the available appointments for their desired doctor: Allows patients to view available appointment slots for a selected doctor.

book free appointment: Allows patients to book an available appointment slot with a doctor.

get a confirmation message through SMS: Sends an SMS confirmation to patients after booking an appointment.

view the booking date afterward: Allows patients to view the details of their booked appointment.

As for the staff:

Log in: Allows staff members to log in to the system to access booking information.

View all the booking information: Allows staff to view booking information for all appointments.

Update and adjust appointment: Allows staff to modify or reschedule an existing appointment.

Sending appointment confirmation to patients through SMS: Allows staff to manually send or resend a confirmation SMS to patients.

Functional requirements:

Patient:

The patient can log in and out.

The patient can view their booking date and see the available booking.

The patient can modify their booking into an available date.

The patient can cancel their booking.

The system will send a confirmation for the patient booking through SMS$.$

The system will remind the patient a day before their appointments

Staff:

The staff should be able to log in and out.

The staff can view all patients' reservations.

The staff can modify the patient reservation when requested.

The staff can update the availability of the booking dates.

The staff will be notified if a patient cancel their booking.

Based on these info draw both a context and Level $0$ diagram $($DFD$)**$keep in mind that the staff is part of the system$**$