Call them & let them know you are on your way. People tend to be more receptive if you let them know that you will be late. If unable to call, still go to the appointment. Even if they do not see the child, you can always reschedule while you are there.
Just get to your appointment as soon as you can. Usually, leave earlier because there is always a morning rush hour or make your appointment a little later morning to avoid the middle of rush hour.
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