Just in case anyone else has the same issue:
I bought a brand new Samsung Note 20 unlocked from the website. I noticed after arrival that the Wi-Fi calling wasn't working. I tried everything I could (enabling wifi calling, have a valid 911 e-address, choosing Wi-Fi as the preferred method of calling, millions of resets, etc.), and nothing was working.
Finally, they contacted T-Mobile; of course, they asked me to do the same thing all over 🤦♂️🤦♂️ nothing worked. Finally, they said to put the phone on airplane mode, turn it off for 20 seconds, and then refresh the Wi-Fi feature on their end and turn the phone back on.
Walla.....it worked. I think I put the phone back on airplane mode and turn on the Wi-Fi to make sure it worked, and it sure did.
I hope this helps anyone that has a similar issue. It's probably the same with AT&T, Verizon, etc.