Default [Q] TMO WIFI calling on ATT G2

You might have seen my previous post regarding which type of rom to install on my unlocked ATT phone which I am using with a Tmobile simcard. Since I have been informed that I can't flash tmobile roms I was wondering if there was a way to install the wifi calling app on the ATT phone (rooted). If it's simply installing the apk could someone please post it on here?