WiFi calling not working

Question

I’m no longer able to send and receive phone calls reliably via Wi-Fi. I’ve noticed other people in this forum have reported similar problems, but Support doesn’t actually help them or fix the issue. My internet is Xfinity gigabit and I have no problems with it. But no one can call me or my wife on our iPhones unless we disable wifi. Really frustrating. 
problem started a few weeks ago after no issues for several months. we’ve tried resetting the phones and resetting network settings. It doesn’t make any difference. WiFi assist is active

SynthpopAddict · Accepted Answer

It's probably an IPv6 conflict.  You'd have to discuss with your ISP about how to disable IPv6 on your router, or else do some technical tweaking so WiFi Calling works.  See the thread below for more details.

https://community.verizon.com/t5/Apple/Wifi-Calling-Issue-on-IPv6/td-p/1803522

SynthpopAddict · Accepted Answer

You're welcome.  I was trying to find another thread where someone was discussing how to set your internet equipment up in bridge mode and avoid double NAT among other stuff, but wasn't successful.  It was a pretty technical discussion.  If I come across it, will post it here.

[update] I found the thread!  Couldn't find it before because it was started with a different question, but fellow Community member Smith6612 appears quite knowledgeable; scroll to the bottom of the thread below for a technical discussion on other tweaks you can do with your internet equipment setup to resolve WiFi Calling issues:

https://community.verizon.com/t5/Samsung/Incoming-calls-problem-Samsung-Galaxy-s25-plus/m-p/1823835#M114807