Issue is resolved by moving to another provider.
Your tech support advised me that me being unable to make incoming/outgoing calls was because of network maintenance (no mention of this on the website) and that it would last 7 days. Noting I live very close to Sydney CBD and not in a remote area, I'm surprised that your customers don't get notified when network maintenance supposedly stops your customers from making or receiving calls, especially when this lasts for over a week.
To top it off, it doesn't seem to be a one off issue, as my partner who had recently moved to TPG also experienced the same issue with Tech Support providing her a different story and her resolution also included moving to another provider.