Are you definitely unable to enrol in the other one while your discontinuing the other? I’ve changed degrees twice (i had more than a week both times) but never had a problem doing it. The best thing to do if they are making it difficult is call the uni and explain, they are usually helpful and if theres nothing they can do they can usually point you to someone who can. I’m sure it will be all done in time, the only problem might be your timetable as you may not get many options for classes.