https://www.verizon.com/support/motorola-droid-maxx-2-update/
Software Version: 24.74.4.lux_verizon.verizon.en.US
Wi-Fi Calling:
You can make and receive calls over a Wi-Fi network, helping you stay connected if cellular service isn’t available.
It's included at no additional charge with your existing plan and device
Use your own phone number to make and receive calls
Wi-Fi calls to US numbers are free, even while traveling outside the US
You can activate Wi-Fi Calling directly on your device. Go to Settings > Advanced Calling > Activate Advanced Calling
Once Advanced Calling is active, you can turn on HD Voice and Wi-Fi Calling from the same settings.
Latest Android™ security updates and bug fixes.