If your application status is ticked submitted, there is little or nothing you can do before admission. First of all; if you are a new applicant and you are not admitted yet, we advise you to wait for admission first. This because a lot processes go through the admission process so if you add an individual request, your application MIGHT be rejected. If your application is accepted and you are given admission letter, go to the faculty of the new course you want and enquire about vacancy, acceptance and directions to change your old course to theirs. This procedure of course changing is more effective when you do it in person then online. Otherwise re-apply for your new course.