Hello Aspirant

It depends upon the university if they have this facility or the guideline in there college.

Usually college under same university do not exempt you from changing the college ,but if you want to change college to a totally different university it might be tough to do so.

Well First check with your college if they have this guideline if so you will have to write a letter and submit to the dean as well as university.If they accept you can change otherwise you won't be able to do so as you had a seat registered.

If you are trying for different state university the only option you have left is appear for neet again ,score good marks and take admission!

Regards!