Late Email Reply

I have been through times when I need instant answer to a critical question, related to an exam and/or an assignment, I have in mind from my instructors. However, there is only one way of communicating between students and their instructors, which is email, and I always have to wait for their reply when I need their answer. The challenge is that there is no way I can contact or communicate with my instructors while desperately waiting for their replies to my email. I know some instructors use social media platforms, such as Facebook, and are friends with their students so that they can communicate there. However, this is not the case with all instructors because they either do not even use social media platforms or they use them, but are not friends with their students. Any of both sides could be the reason why they are not friends. Despite all this, communicating on social media platforms is not professional. Therefore, I would recommend AUIS to provide each instructor with a work phone number, which students can use to contact their instructor in necessary cases.