"34. Prohibition of night work.
(1) Except in accordance with regulations made under this Act or any exemption granted under the proviso to this subsection no employer shall require any female employee to work in any industrial or agricultural undertaking between the hours of ten o'clock in the evening and five o'clock in the morning nor commence work for the day without having had a period of eleven consecutive hours free from such work:..."
Although female employees are not required to work in industrial or agricultural undertaking between 10pm and 6am without approval from the Labour Department, employees in call centres like your are not covered by the said subsection(1). Call centres don't come into "industrial and agricultural" undertakings which are places like factory or rubber estate. So, you can be required to work night shifts without your employer having to get approval. As such, females employees should be careful about their personal security working in those hours especially going/returning from work. The car park may be deserted and you don't know who are lurking around.