hello Furqa,

Yes, you can always cancel your seat in whichever college or field yo have got but there are certain conditions.

if you have selected the seat in college you can cancel it and if you have paid the fees and you want to leave college then the refund of fees depends on the college refund policy.

many people do this, some change their stream from engg to medical also.

it is legal and the process is not so hard.

hope this may help you.