Home Internet & Wifi calling

Seems like we have an issue similar to the above.

We have T Mobile Home Internet and all our phones use T Mobile sim cards and were purchased at the T Mobile store.  Our T Mobile Home Internet gateway is the Sagemcom device.  When inside our home, our phones only have one bar of signal clarity.  So the WiFi Calling feature is something we desperately need.  I have tried countless ways to get WiFi calling to work.  I have reset our phones, and the Sagemcom.  But each time we try to make a WiFi call, we get the message "No Network Connection.  Connect to a WiFi network" even though it is clearly connected to the Sagemcom WiFi.  

I also switched out our Sagemcom with the Nokia gateway, after reading that the Nokia might be better.   I used the sim card from the Sagemcom and the Nokia gateway worked great.  But still had the exact same WiFi calling troubles.    

However, the one ray of hope I have is that WiFi calling somehow does work on one phone: a Samsung Galaxy S22.  When I set it to Airplane Mode and WiFi Calling On, it can send and receive calls with no issue.  Clear calls!  So nice!  It is the only Andriod phone we have.  The rest of our phones are iPhones from new to old.  So now am thinking this is an issue somewhere between iOS and T-Mobile Home Internet.  Has anyone seen something similar?  

I've called T-Mobile a number of times, each time getting a different response (ranging from apparently supportive to astonishingly uneducated).  So I'm not convinced T Mobile is taking this seriously or has an active project to study and resolve.  I appreciate all the comments above, which gives me a sense that we are not alone in this concern.  We love TMHI, but not having WiFi calling, something that should be basic, is causing us to think about other options.