Hello friends,
In most of the cases the filled value cannot be changed and altered. Also it would be more helpfull if you have mentioned the examination. Kindly carefully fill the form when you fill it for the next time. Also try to contact the customer care or help page of the particular examination and write an email to the authority. If possible they will definitely help you or you have continue with the same credentials.

Please specify exam.But mostly if you submitted the application then you can't.But you can contact the officials for further instruction.