Not receiving calls or VM on Wi-Fi & call audio issues on Wi-Fi -- iPhone 16ProMax/iOS 18.5

Since I upgraded my iPhone 12ProMax to a 16ProMax in April 2025 I've been having call dropping issues and call audio issues pretty consistently.  If I'm on Wi-Fi, audio often drops during my call regardless of whether I'm using AirPods Pro2, speaker phone or holding the phone to my head - the common denominator is that it's on Wi-Fi calls.  While on the call, the other person can hear me, but I can’t hear anything until I turn off Wi-Fi and audio is instantly restored.  This call audio on Wi-Fi issue has been consistent since I got the phone regardless of updates, network resets etc. and continues with iOS 18.5 as of today.    

Fast forward to the last week or so, now I'm no longer receiving calls or call notifications when I'm on Wi-Fi and I am no longer receiving voicemails or voicemail notifications when said calls go straight to voicemail.  If I hard-restart my phone, it seems to be ok for a short time, but within an hour or so I received a text again that someone else had tried to call me, got my VM and left me a message -- no call, no missed call notification, no VM, no VM notification.  I have restarted my router, “forgotten” my networks and re-added them on my iPhone, reset my network settings to factory on my iPhone, toggled airplane mode on and then off again, toggled my cellular networks off and back on again, turned off Wi-Fi calling and back on again and ensure all apps are closed in the background.  I am on the latest version of iOS (version 18.5) and the issue seems to be getting worse. I have also confirmed that Focus/Do Not Disturb modes are not active and that call forwarding is not active.  

I’m finally starting to see people with the same call issues show up on the Apple community support pages, but none have mentioned Wi-Fi specifically as a common denominator for when it’s happening.  My current temporary solution is to keep my phone’s Wi-Fi turned off to ensure I can receive calls/VMs, but this is not a sustainable solution. 

FWIW, when I first got the phone in April of this year on version 18.4, I was also dropping calls where the call would not reconnect until the 3rd attempted re-dial, but that bug seems to be finally fixed with iOS 18.5 update.

These bugs are not happening on my wife's iPhone 16 Pro or my mother's iPhone 13.

DEVICE: iPhone 16 ProMax

SOFTWARE VERSION: iOS 18.5 (current version)

CARRIER: Verizon Wireless