Hello,

This is something unfortunate.There is only one thing to do, rush back to your respective exam centre if it is in your reach, if not you are not allowed to write your exam.In no way you are given an another chance to rewrite the exam.So candidates are responsible for their unfortune.It is advisable to visit the exam centre one day before the exam so that you won't go to the wrong exam centre on exam day.

I hope this helps.