Truphone QUIT from Australia!!!!! There's no alternative service provider.
I bought my son an Apple Watch Cellular and been told Truphone provide service for him to have his own number without a phone. I called Truphone be told they won't provide such service for Australia anymore. I consulted all rest carriers Telstra/Voda/Optus, none of them provide similar service but have to sign a plan minimum $40/m and must have an iPhone sync with it. Which means extra $480+ an iPhone Cost. Can I return the watch and get refund!? Much much cheaper to buy android watch.
Set up cellular on Apple Watch – Apple Support (AU)
You can set up a cellular Apple Watch for a family member who doesn't have their own iPhone. If your mobile carrier supports the use of a managed Apple Watch, you're given the option to add the watch to your plan during setup. Look for the option to set up cellular, then follow the onscreen steps. If your service provider doesn't support it, you may be able to use an alternative service provider.
Apple Watch - Carriers - Apple (AU)
Family Setup
Compatible Models
Apple Watch Series 7 GPS + Cellular
Apple Watch Series 6 GPS + Cellular
Apple Watch SE GPS + Cellular
Apple Watch Series 5 GPS + Cellular
Apple Watch Series 4 GPS + Cellular
Country or Region
Australia
Supported Carriers
Truphone