Hello Dhruvi,

 In case the mistake has already been done please send a revised application form , if there is still time . Otherwise , write an application to the appropriate authority appologising for the mistake and offering to correct it . Enclose necessary documentary proof of the correct catagory in which your caste is categorised.Act immediately. (Though there are doubts this will work.)

You can still take the exam through the unreserved category and secure a seat with that. But you will not be able to avail the benefits of reservation. You can still claim for a seat in open category. 

All the best.