Yes you can upgrade your branch in JOSSA counseling. For that you need to wait for next rounds of counseling. 

For this firstly you need to go to respective college where you have grabbed the seat. Then you need to pay the fees for admission. Now their is a option of Sliding. Sliding in being used in JOSSA counseling for the cases when you get the college but you want different branch in same college. So if you went for Sliding option, then if in next counseling you get the seat in your desired branch, then you will be automatically shifted to new branch without much of task to be done