Whenever I go I take 2 iphones. My current iPhone with my uk sim I keep on but switch of data roaming. When I arrive I buy a Telstra prepaid SIM card with $30 credit and put that in my old spare iPhone and use it for all my Aussie calls texts etc and tether my uk iPhone to it so it has data as well. Alternatively use one phone and take your uk sim out and replace it with the Telstra sim. I find the 2 phone set up best for me. Telstra is not the only choice of network you have but I find it has the best network coverage in rural Australia which is what I need. I hope this helps and have a fantastic time