Hello

Aspirant

Firstly Calm down yourself, Don't take tension if you accidentally fill the wrong roll no.  their is nothing to worry about. If you written your other details and roll number in words correctly so, Nothing to worry about!

And if you fill wrong roll number in OMR sheet so your OMR sheet will not gonna be rejected if you fill correct roll number at the top because your OMR will not be read by the system but then the operator will check it out and hence fill the correct roll number in the system.

For the double check you can directly contact with NTA which conduct the NEET Examination.