Wi-Fi Calling is an enhanced calling feature, which allows you to make and receive HD voice calls, send/receive texts and pictures (MMS) using a Wi-Fi connection rather than a cellular connection.
Think of Wi-Fi Calling as a backup option when your cellular coverage is less than perfect. For example, inside buildings and basements that have Wi-Fi service, but cellular signal is weak or unavailable. Once you enable this feature, your phone will automatically switch to Wi-Fi Calling under these circumstances.
* Use of Wi-Fi Calling may be restricted in some international countries.
To be eligible for Wi-Fi calling you need to:
*Tap Settings > General > About Carrier. If an update is available, you'll see an option to update your carrier settings.
** Tap Settings > General > About > Software Version. If an update is available, you'll see an option to update your software version
To turn on Wi-Fi calling:
You will be required to:
Follow the onscreen instructions to enter or confirm your address for emergency services.*
Note: You will automatically see “Wi-Fi” after the U.S. Cellular name in the status bar if you’ve activated this feature and cellular coverage is poor or unavailable.
*When cellular service is available, your iPhone uses it for emergency calls. If you turned on Wi-Fi Calling and cellular service isn't available, emergency calls will use Wi-Fi calling. Your device's location may be used to aid response efforts when you place an emergency call, regardless of whether you enable Location Services.
Set Emergency Address on iPhone
Important - Emergency 911 Call Limitations
When calling 911, always tell the operator where you are. Your 911 call will go over Wi-Fi only if the cellular network is unavailable. A 911 call made over Wi-Fi may be delayed or unsuccessful; for example, if the 911 system doesn't recognize the address, electrical power is out or your Wi-Fi connection isn't working. Emergency service will be sent to the address you provide above, so please update it as you change locations.
Some business organizations may have firewall policies that restrict incoming UDP from the public Internet. These businesses will need to contact their IT department administrator in order to allow Wi-Fi Calling to work properly, and the following UDP ports will need to be allowed through the firewall. Outgoing TCP connections on the listed ports will also need to be allowed.
|IP Range||Port Num (TCP/UDP)||Description|
|126.96.36.199/20||Port: 500 / UDP||IPsec - IKE : Device Authentication|
|188.8.131.52/20||Port: 4500 / UDP||IPsec - NAT traversal : Encrypted voice traffic|
|184.108.40.206/20||Port: 5060 & 5061 / TCP/UDP||SIP/TLS : Call Signaling|
|220.127.116.11/26||Port: 443 / TCP||TLS : Voice over WiFi Service Activation|