Hi,

Yes you can cancel your admission now. But you have to give some amount of fees which is called penalty fees. Because no college is agree with you after admission cancelling admission. Because you reserve one seat , if you didn't take that seat then any other candidate could chance for admission who is desperate for admission. So you can talk to your college authority for cancellations of your admission and pay amount leaving fees. Then you can leave your college.  For this, you must first check out the refund policy of your college. Some amount of fee will be returned to you with minor penalty deduction (refund policy varies from college to college). If you cannot find any refund policy of the college, kindly visit the officials for information about same.

Hope this helps.