You can unsubscribe by logging in to the educational administration website directly on your mobile phone and selecting teaching materials. If the page can't be displayed, it is that the function of the mobile phone is not working. Actually, there is no need to unsubscribe. The school makes all the books bought useful. By default, all books are reserved, and there will be no extra charge. Old books bought outside school are not necessarily the same as new books, and the same ISBN version will be different ~ so think carefully.