If you want to make a change, it should probably be as below (or it can go as it is).
Notification of New Timings
This is to inform all our staff members that the timings for each of the following functions at ________ Center will be as under with effect from [B][\/B]* (Date). The staff members working for each of the departments must be at their designated workplaces by that time. You are all requested to strictly follow the timings to maintain discipline and ensure customers are not inconvenienced.
Override of Previous Communications
(You can add if you want:) This circular will override all previous circulars, letters, and communications regarding work timing for each of the staff members of the concerned center.
Lunch Break Policy
Please note that a 30-minute lunch break will be given to the staff members, which should be used/adjusted in such a manner as to not leave any station unattended and keeping in mind the flow of patients and pending work.
Contact for Queries
In case of any doubt or problem, you are required to approach Mr. [B][\/B]**, Center Supervisor directly.