Its dependent on the board or technical council you are studying in. So anything conclusive can't be provided as you didn't provided the information about it. In general such things can't be done after the admission take. Now you can change your field to BTech IT after your Diploma through lateral entry entrance, it can be done. But in your diploma it can be done or not, is dependent on your council or college.

To know more about BTech Lateral Entry visit the link below:

https://engineering.careers360.com/articles/what-btech-lateral-entry-eligibility#:~:text=Tech%20lateral%20entry%20is%20the,first%20two%20semesters)%20of%20B.

I hope this answer helps. All the very best for your future endeavors!