Default [Q] T-Mobile Wifi Calling

Hey everyone. Well, I just have a question. I was doing some research on this but couldn't find what I needed.

I have the Sony Xperia Z1 (c6903) and I'm currently on T-Mobile and wondering if there is any apk for the Wifi-Calling? I don't want to flash a rom on my phone, but so far that's the only way, at least from what I read. Pleassee correct me if I'm wrong, it would be the best Christmas present ever! =P

Thanks!
Carrier: T-Mobile USA
Device: HTC HD2
ROM: T-Mobile Stock ROM 2.13.531.1
Radio: 2.10.50.28_2