When I crossed the Great Dividing Range into western Queensland I soon found that my mobile telephone no longer worked. It is such a common problem that the tourist information centre I visited had maps on hand to explain it all - only Telstra works outback. Only Telstra SIM cards are sold at the shops.
Years ago I had transferred my number from Telstra to Belong (a discount brand from Telstra) in order to get more data at a reasonable price. I had thought that Belong - being owned by Telstra would work. I was wrong.
In the meantime Telstra now includes a enough data for my purposes in its plans (not a huge amount) so I have switched back.
Early in my career I was a member of the team that automated outback communications with the Digital Radio Concentrator System. I enjoyed seeing the tall masts in remote places.