Dear Student,

Not in BIT but also in any college you can change your branch but you will not be allowed to change your whole course.

As here you are talking about to change from Msc to B.tech so that would not possible. You can change your subject of your course after the 2nd year but can't change your course.

Or you can cancel your admission from Msc and then take admission in Btech course but here you also need to start from 1st year again.

Good Luck :)