Hello Aspirant,

Changing stream might be possible either before the commencement of the course or in the first year of the course. Post first year it is not a wise decision to change streams .Especially  in this case , degrees like BA and BSc are of 3 years duration ,so it will not be helpful to change in the middle. Also , you should contact the university directly and ask whether this provision is possible.In some universities this might be part of their college policy and in others , it will depend on the decision taken by the respective department heads , so kindly contact the college administration or the heads of the respective departments to about its procedure.

https://www.careers360.com/colleges/rd-and-dj-college-munger

All the best