Dan Thorp-Lancaster, writing for iMore:
To enable the feature, you can navigate to the “Phone” section of your Settings app and flip the switch next to”Wi-Fi Calling.” You’ll then be taken through a series of setup screens where you can set your 911 emergency address and then activate the feature.
I usually spend Christmas and Thanksgiving day visiting my fiancée’s parents. And while we’re there I always end up talking on the phone for 20-30 minutes with my mother and siblings. We talk about what our plans are for the day, the gifts we’ve received or given, what we’re having for dinner, and other various topics. But my fiancée’s parents live in a dead-spot for cellular coverage and I end up having to seclude myself near the front door to sustain the phone calls. Having Wi-Fi calling turned on will solve that problem — I’ll be able chat with my family in the comfort of my future in-laws living room without worrying about losing the connection.