Telstra One and Apple Watch

Hey 24Lana,

Thanks for using Apple Support Communities, and congratulations on your new Apple Watch! When setting up service for a new Apple Watch, you'll want to complete the steps under "Before you start" to make sure all updates are installed, including carrier updates and that everything is ready to get cellular set up: Set up cellular on Apple Watch - Apple Support

Before you start

* Make sure that you have the latest software on your iPhone and your Apple Watch.

* Check for updates to your carrier settings.

* Make sure that you have an eligible cellular service plan with a supported carrier. Your iPhone and Apple Watch must use the same carrier,* and you must be within your carrier's network when you set up cellular on your watch.

* If you have an enterprise or corporate cellular service plan, check with your company or carrier to see if they support this feature. Pre-paid accounts and some older accounts aren’t currently supported. To make sure that your account is eligible, contact your carrier.

* An Apple Watch that you set up for a family member can use a different carrier than your iPhone uses.

After ensuring those steps are complete, see if the steps under "Transfer your cellular plan to a new Apple Watch" help with activating your service.

Let us know how it goes.

Take care!