At least Telstra offer a check service in case you have an older 4g phone. Some discussion that some models could be affected for 000 calls.

SMS THE NUMBER 3 to 3498, we received an" ok " message shortly after doing so.

Thanks for that ...

Worked for me too. 

Got a much longer response identifying the mobile number & iPhone model as well as confirming that it was 4G capable ...  &  saying thanks for using the service.

Worked for me too.

Checked two phones today. One isn't ok & the message said the 3g cutoff is 30 June.

The other phone is ok & but it still stated the cutoff date, but it was 31 August.

Can't see why two different dates.

I have a silly phone for old farts. Just recently I lost the facility to make and receive voice calls, but SMS and time syncing via the network were unaffected. Apparently, this happens if VOLTE is disabled. This was a common problem after the switch from 3G to 4G. I don't know why, but I had to reboot my phone to re-establish VOLTE, despite having no problems with it for several months.