Wi-Fi Calling is a relatively new feature for iPhones which takes advantage of the WiFi network you are currently on to make phone calls when your cell service sucks. Previously you would have to use something like an AT&T MicroCell or a Verizon Network Extender but these devices are not obsolete and everyone can get the new Wi-Fi calling for FREE. It works way better than the old method which only worked at your own home and lets you make calls on any Wi-Fi network where your cell service is not good enough. Best of all: calls are crystal CLEAR.
Here's how to enable it:
- Go to Settings -> Phone -> Wi-Fi Calling
- Turn it on and go through the prompts from your carrier to enable the service.
That's it! Now every time you have poor cell service you should see "Wi-Fi" next to your carrier name in your status bar of your iPhone. AT&T and other carriers will soon also enable support for your other iOS and Mac devices to make and receive phone calls with your iPhone's number even when the two aren't near each other.
If you're on Verizon, hang tight as this feature is not yet available but should be relatively soon.
Read more on Apple's support document about the feature: https://support.apple.com/en-us/HT203032