Hey,

it may only be done when you have correction window open , at that time only your exam center may changed.

and yes it is also not sure that it may be your preferred location as you may only get your preferred  location when their is availability of seats.

Hello,

First check out if center correction window is open for the entrance exam which you will appear. if yes then there will be link available to change and instruction to follow so that you won't get confuse and fill the correct details.

It is important to get accurate details from the right source. as you have not mentioned which entrance exam you will appear it is hard to say if there is any provision for correcting exam centers. Please help with the exam name so that i can provide you the details.

Hope it helps!