All you need to do beforehand is make sure that your iPhone is set up to listen for the "Hey Siri" voice command. You can check this by following the steps below:
Enable the "Hey Siri" Command on Your iPhone
- Launch the Settings app on your iPhone.
- Tap Siri & Search in the list.
- At the top of the screen, check that the Listen for "Hey Siri" slider is toggled to the green ON position.
What if the person you want to call isn't in your contacts list? No problem – just dictate the number to Siri instead: "Hey Siri, call [number] on speaker."
Remember this quick tip the next time you want to make a call and you might just save yourself some bother.