Dear aspirant....!!

Yes you can change the course if and only if you have not done the payment and the choices you have filled in the form for your course like if you have filled Bcom, Bcom hons, economic Hons, English so you can't take admission in hindi hons as you have not filled the option you can probably change the option if you have not done the payment.

Also it is possible to edit your application form till the last date of registration but only if you have not paid the fees.

If you have already paid the registration fees, then the DU portal will not allow you to make amends.

All the best!