iOS 8 introduced Wi-Fi Calling, a new feature that allows your phone to connect to your cell phone company (currently only T-Mobile) over Wi-Fi rather than via the cell phone tower. This allows you to place a cell phone call where your cellular signal is weak or non-existant, even avoiding roaming charges if connecting by Wi-Fi internationally.
- Supported carrier. Among American carriers, currently only T-Mobile supports Wi-Fi calling, though AT&T and Verizon have said that the feature will arrive in 2015. Sprint supports Wi-Fi calling from several Android phones but has not yet announced support for iPhone.
- Supported phone. Only the iPhone 5c, 5s, 6, and 6 Plus are supported.
Visit the Settings app > Phone > Wi-Fi Calls. Turn on “Allow Wi-Fi Calls”. When your phone is connected to WiFi, it will attempt to connect through Wi-Fi instead of cellular. Note the carrier name. It will switch from “T-Mobile” to “T-Mobile Wi-Fi”. When it does you can ignore the cellular signal meter. The Wi-Fi signal meter is what matters at this point.
If you have any trouble, you may need to call T-Mobile customer support (611 from your cell phone).
- Enabling Wi-Fi calling disables a new feature in the upcoming OS X Yosemite that allows you to answer phone calls from your Mac.
- Calls can’t or have a difficult time switching from Wi-Fi to cellular and vice versa. So if you walk out of your Wi-Fi range your call will probably be dropped.
- If you have a good cellular connection but the Wi-Fi network you are connected to is slow, you might have better luck disabling Wi-Fi before placing your call.
- Calling 911 could be problematic because the call will appear to originate from your billing address (unless you changed your emergency address) and could be routed to the wrong call center. If you must call 911 and you aren’t at home it’s best to do so when your phone isn’t on Wi-Fi calling mode. Turn off Wi-Fi if needed.
- There is no option to only enable Wi-Fi on particular networks. Any time you have Wi-Fi access your phone will attempt to switch modes.
- If you don’t have an unlimited calling plan, Wi-Fi calling still uses your minutes because you’re still using their phone system, you’re just accessing it a slightly different way.
- If you will be somewhere that you absolutely do not want to use cellular, such as when traveling internationally, you can put your iPhone into airplane mode, then turn on Wi-Fi (which airplane mode just turned off). This will keep the cellular radio off to avoid roaming charges yet you can still make calls over Wi-Fi.
- Enabling airplane mode and turning on Wi-Fi might help you to save battery power in fringe areas where your phone is using up lots of power trying to connect to a weak cellular signal.