For Christ University, my first preference was Bangalore campus but I got selected for Delhi, NCR, can I change my campus to Bangalore Christ University?

No, that is an option you do not have. Once you’re admitted to a particular campus and are done with the procedures for getting admitted, it is impossible that that could happen. To be precise, once your admission number is generated for the place of your choice, it is illogical for anyone to be opting otherwise (you can always re-apply).