If you wanted admission in one college but your seat got allotted in another college during the counselling process then you will need to follow the next round of counselling or upgradation process if available. In many counselling systems there is an option called float or slide or upgrade which allows you to wait for a better college in upcoming rounds. But if the option is not available and you have already taken admission in the allotted college then you might not be able to shift unless you participate in fresh rounds or management quota. You should also check with the official counselling portal or helpline to know if any special procedure is allowed for changing colleges. It is important to stay updated with official announcements. You can also try spot round if it is conducted later.