Apple Watch plans on separate carrier
Will the watch work with cellular and gps on a separate carrier than my iphone?
Question marked as
You must have the same carrier on your Apple Watch cellular as on your iPhone, unless you set up the Apple Watch for a Family member:
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- 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 using Apple Watch For Your Kids (formerly known as Family Setup) can use a different carrier than your iPhone uses.
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copied from: Set up cellular on Apple Watch - Apple Support