Once you froze your alloted seat it is notified to the cet server that this person has selected the alloted seat and wont be participating in the further round and therefore you name will be cut from the list , while freezing the there was an option for going for betterment pupil should select that option incase they want a different option other than the alloted one. If a seat is frozen in your name now ,you should visit the college and the authorities for further guidelines and incase you want to go for a different college option visit the college and enquire about management quota.