My wife worked in Australia for large chunk of 2019 and made long VOIP calls from there without problems. What kind of phone does the person have? With a modern dual SIM IPhone, I would look at TextNow purchasing their optional SIM and paying the $25 a year for no adds and to keep the number. Using their soft client, you can VOIP and text from Oz just fine. When you visit the US, put their SIM in slot 1 and purchase an optional data package from Apple for your data.
Originally Posted by
YuropFlyer
You'll have the latency due to lightspeed taking a while from the US to Australia. It's impossible to have 30ms on such a distance.
It's not the lag from his computer/phone to the local service provider, or having slower internet, it's simply the time (in milliseconds) the data packets take from some point in the US to some point in Australia.