Dear Student,

You can change only if the correction window will open and it it will not open then you can't do anything.

As you have selected EWS and you don't have the certificate of EWS so in further steps if they find that mistake then they will put you in the general category and in the whole academic year you will counted as general candidate.

Another thing you may try is that write a letter directly to the officials and ask about your problem and solution, they might provide you the best solution.

Good Luck :)