FYI the latest posts on that MS thread give you the steps to supposedly get it working right now. Can anyone try this and confirm if they've had success?
Call in, get Wi-Fi calling added to your account, get special sim card, hard reset? Well, having Wi-Fi calling added to your account is either because it's in a testing phase right now, or T-Mobile is guarding it by making you call in to get it. The way it's always worked is you got Wi-Fi calling as a software feature to make calls using your minute bucket (no calling in or talking to customer service, it just WORKED on Android), and you call in to get the plan to allow unlimited calls over Wi-Fi that don't take away from your minute bucket. Unless that process has changed, of course. This was back when there were actually minute buckets - doesn't really matter, now
I've hard reset my phone too many times already for random stuff. The last time I did it, I lost access to both iheartradio and USAA since they got pulled from the WP8 marketplace- and USAA is never coming back. Not gonna do it again unless multiple people can confirm this on an 810. This is a very important feature and one of the reasons I've been happy on T-Mobile.