Have you considered Aldi Mobile? They use the telstra network with some towers excluded. I don't know if there's a way to look up what towers are excluded, but I was under the impression that it was remote towers where no competitors service.
I'm 100% for making stuff, Just be careful with makeing stuff like this, something to do with emergency/military signal interference can land you in the shit from what I have read, but if you got the skills and knowledge, bloody get em
Literally any MVNO is better than Telstra, Optus, or Vodafone. Go with Amaysim, Boost, Yatango, Vaya, one of the supermarkets' mobile plans. Shop around. Most of them use the Optus network, but some are on Telstra.
I live in shitty small city and a have shitty connectivity. Luckily, fiber is available and my phone has something called Voice Over WiFi in phone settings. Day & night difference to me. See if this helps you too?