WiFi Calling not working suddenly

I've fought this problem for hours over the past several months on both my phone and my wife's.  They even sent me a hot spot tower and it's didn't work either.  I've finally made the decision to go to another carrier.  I don't know what the problem is and apparently T-Mobile doesn't either but I never had this problem before I switched to T-Mobile.  I realize not that is was a mistake on my part.