Hey,

Yes you can change your registration details after the free payment but only partially as few fields can't be changed.

As you have not mentioned the name of the exam so it's difficult for me to tell you the fields you can alter or edit after the fees payment.

If you ket me know the name of the exam then I will tell you the fields you can edit once the correction window opens.

Wait for the notification of opening of the correction window and then edit whichever is editable.

Hope that helps

Thank you