I don't know which examination you are talking about. But if you have been provided the exam centre and the hall ticket then you can't change the exam centre. So exam centre can't be changed. It's a policy for most of the examination and entrances.

If you want a more specific answer, I would recommend you to repost the question with the name of the examination so that we can provide you all the required information as soon as possible.

Have a great day!