why siri on my i phone seven plus wont work

To start getting calls on one of your devices, just turn On the Calls from iPhone setting on that device. Watch the GIF

Watch the GIF below

You can use iPhone Cellular Calls with any Mac, iPhone, iPad or iPod touch that meets the Continuity system requirements. It works when your devices are near each other and set up as follows:

1. Each device is signed in to iCloud with the same Apple ID.
2. Each device is signed in to FaceTime with the same Apple ID.
3. Each device has Wi-Fi turned on.
4. Each device is connected to the same network using Wi-Fi or Ethernet.
5. On your iPhone, go to Settings > Phone > Calls on Other Devices, then turn on Allow Calls on Other Devices.
6. On your iPad or iPod touch, go to Settings > FaceTime, then turn on Calls from iPhone.
7. On your Mac, open the FaceTime app, then choose FaceTime > Preferences. Click Settings, then select Calls From iPhone.