I followed how to instructions....after 5 tries....
It's installed but no matter what anyone says the 810 doesn't support it. If you're calling via Wi-Fi it will say on the bottom of dialer tile, and on the Wi-Fi tile it will indicate ready, when you're making the call Wi Fi Calling will be on the upper left hand corner of your screen. None of those Wi-Fi connected or calling indicators appear. If you're getting more bars -you're getting better reception not Wi-Fi. Cool app if it really worked.
I'm next to the Wi-Fi router turning Wi Fi calling ON or OFF the bars are the same, 2bars @ 4G and sound quality is the same. I live at the beach and a Naval Air Station and cell towers have to be a certain distance away and reception is really poor.
If I set it to Wi-Fi Only I "can't" sent text, yet I can, if I set it to Wi-Fi Only a Wi-Fi network must be present and within range to make calls, I turn off the router or go outside where I'm out of range I can still make calls in both cases.
This doesn't work with the 810, it doesn't support Wi-Fi calling even if you think that the Wi-Fi indicators won't show because it wasn't designed for the 810, fine that makes some sense, but if I can make calls or text with it set to Wi-Fi Only when the router is off or I'm out of range then it doesn't take a genius to figure out it that it doesn't work with the 810. FYI I keep the app open when I make a call and it's set at Wi-Fi Only and the router is off, I toggle back to the small screens and I can see the app and the call dialer on the same screen and it's dialing and it goes through and connects and it's Wi-Fi Only with the router off.
On May 20, a software update to Software version 1030.6409.1316.0016 was released for the Nokia Lumia 521. The software update, which will be available by Over The Air (OTA), will add Wi-Fi calling.
Unless you've had an update to enable the 810 to have Wi-Fi calling then all you have is a nice blue tile on your phone that does nothing.