With Traveloka's Sim4g, I installed the sim when the plane was about to land in Melbourne. When I got to the airport, the sim still didn't work. I had to turn off and restart my phone many times. I wondered if it was because I bought the sim in advance and registered for the 4g sim's active time of about 5 days but the server didn't update or if the sim was faulty. After that, I also selected some Australian carriers and finally when I got on the bus from the airport to Melbourne city center, the sim was active and since then the 4g signal has been quite stable, even when I cycled to the countryside around Melbourne.