https://www.verizonwireless.com/support/wifi-calling-faqs/
How do I enable Wi-Fi Calling on my iPhone®?
To activate Wi-Fi Calling, you must be connected to the Verizon Wireless data network to turn on Wi-Fi calling.
To enable Wi-Fi Calling on your iPhone:
First, verify that you meet all of the eligibility requirements.
Turn on Wi-Fi Calling:
Go to the Home Screen.
Tap Settings.
Tap Phone.
Tap Wi-Fi Calling.
Tap or slide Wi-Fi Calling On This iPhone. (slider will be green)
Tap Enable
Follow the onscreen instructions to enter a US address for use in the event of an emergency call (911).
Once your address is saved, the Wi-Fi Calling setting will be turned on. You are now able to take and make Wi-Fi calls on your iPhone.
Who is eligible for Wi-Fi Calling?
To be eligible for Wi-Fi Calling, you need to:Have a phone that's HD Voice-enabled and Wi-Fi Calling-capable.
All currently available smartphones are HD-voice-capable.Have the HD Voice feature on your account and activatedNote: If you have any features that are incompatible with HD Voice, you'll need to remove them before you add the HD Voice feature to your account. Find out about which features aren't compatible with HD Voice, or learn more about HD Voice and how to activate it.
My phone number is on a business account. Can I use Wi-Fi Calling?
Yes. As long as your line already has HD Voice and doesn't have the "Block Wi-Fi Calling" or the "Voice Block" features on the account.
