Make and Receive Phone Calls
If you have a cellular Apple Watch, you can place and receive phone calls directly from your wrist, even when your iPhone isn’t nearby. This uses your cellular number and plan from your paired iPhone.
However, the iPhone doesn’t need to be on for this to work. Incoming calls will ring on both devices and can be answered from either. Further, despite your iPhone and Apple Watch sharing the same phone number, it’s actually possible to have two phone calls going on at the same time. In other words, you can still place calls on your Apple Watch even if someone else is using your iPhone.
Depending on your carrier, this may work on non-cellular Apple Watch models, too, as long as you’re connected to Wi-Fi. If your carrier offers a compatible Wi-Fi Calling service, you can place regular cellular calls even from a Wi-Fi-only Apple Watch. If not, you can still place FaceTime Audio calls.