Telstra is repurposing some of its 850Mhz Spectrum for 5G, however there should be no material detriment to 3G voice calls.
Seniors' guide to the 3G shutdown - National Seniors Australia
Upcoming 2G and 3G Global Cellular Network Sunset Dates
3G Shutdown: 6 Things You Need to Update & How Much It May Cost
Old cell phone? End of 3G means you'll likely have to upgrade soon
Comms Business - BT switches off last 3G mobile site
Millions of Devices Could Lose Service as 3G Shutdown Begins - The Plug - HelloTech
How Will A Person Know If Their Phone Will Be Affected By 3G Shutdown?
What is the 3G switch-off? How to find out if your mobile phone
Switching off the UK's 3G mobile networks: what you need to know
We're Switching Off Our 3G Network
Vodafone UK successfully retires 3G in Basingstoke and Plymouth
The 3G Shutdown: How Will It Affect Your Phone?
What happens after the 3G network dies