Well, brother it is tough to say that you should go to branch change or not, as it is not that easy to what aspirants think.

Regarding branch change, pne thing is in your favour that IIT KGP allows maximum branch change among all th IIT's, so this is in your favour.

Still, if you can't convert yoru branch then you would be in a fix/problem

So, I would recommend you to study/overview all the academics that appear in the first year of engineering college, so that you can be confident about oyur decision.

All the best for yoru future endeavours.

Thank You