Hi there,
Hope you are doing well.
I am really sorry to say but once you have filled your preferences for JAC counselling, you can't change them.
They remain as they are, for the remaining rounds of counselling and there is no way you can alter them.

But if you have freezed your seat and taken admission in the branch and don't want to sit for further rounds of counselling, then you can contact the college authority.
Or there is always an internal sliding of branches after the first year, you can change your branch at that time.
Hope it would help.
Thank You