Department of Immigration and Citizenship - South Australian State Headquarters

Hi, my student visa 500 expire today. I have submitted the application to your office via speed express yesterday and when I tracked my letter it’s already been delivered to your kind office today morning at around 0749 hours.I am very worried and running out of time so kindly advise what to do next. I am hoping to get the acknowledgment letter via email from your office today before office hours so that I remain lawfully in this country. Your immediate response will be highly appreciated. Thank you. With regards