WiFi calling definitely comes in handy for a lot of users and for the ability to customize it to go away after an update can be pretty frustrating. I read the link you provided along with perusing some other forums and a lot of users are talking about the lack of WiFi calling settings being built into the latest Android update. Unfortunately, we don't carry that specific device and don't have a lot of control over the update.
Just to clarify: T-Mobile isn't doing anything specifically to have changed the functionality its just a bug in the software released by BlackBerry Mobile. Right?