u already have a valid deferment until Mar 2020. Therefore, u do not need to do anything in 2019.
the only time u need to apply for deferment is when u need additional semesters to complete your current studies (in the event in which u had failed your subjects or due to medical, compassionate grounds that requires extension only).
do note that deferment to further your studies (e.g dip to degree, or into a different major) will not be allowed.
lastly, please work on your numerous typo errors in expressing your enquiry. Or is this how your private school's standard of english is?