How do I prevent incoming call notifications on a non-primary iPhone? I am using an iPhone 6S as my primary work iPhone. I have an old iPhone 4 that I am trying to use as a dedicated baby monitor.

The iPhone 4 has had its SIM card removed, but it maintains WiFi access to our network.

Both are using the same apple ID.

Whenever my iPhone 6S receives a phone call, my iPhone 4 still shows an incoming call. I have gone into phone notifications and disabled everything. I'm not sure what else to disable to prevent it from ringing. Any ideas?

Both are running the latest IOS (10.3.1).
I have had this same problem, and fixed it by first turning off iCloud Drive. This fixes the shared call history between devices. Second, go to Settings -> Phone -> Calls on Other Devices -> Off This fixes calls ringing up between devices

In your case, you could also avoid the problem by turning on Do Not Disturb on the iPhone 4 — that will stop all notifications. It is found in Settings -> Do Not Disturb