My phone (Galaxy S9+) will go straight to voicemail (intermittently) , even though I have an old 3G network extender AND I have the phone set up to use Wi-FI calling. This has happened intermittently for over 3 years. Originally, Verizon Tech Support sent me the extender and it worked until I upgraded phones. Now, on occasion, I will get the message "Network Extender" on the bottom of the screen. I DO NOT constantly get the icon telling me that I have used my Wi-Fi router. I get 1 or maybe 2 bars from the Mobile network even though I live in a very highly populated suburban area. And, of course, the "web maps" show I have excellent service, which I do not and have not had for the time I have been on Verizon. The phone will intermittently show I have 4G service and sometimes it will NOT show I have that service.
To be honest, this is getting to be a real pain. Why can't you just upgrade the phone network in my area and solve the problem??