I have disabled option VoWiFi (wifi calling). But when I was connected to WiFi in home and I am was calling to someone during call I checked quick panel. I noticed that wifi calling was dimmed blue, not blue like Wi-Fi but in half blue. When I ended call wifi calling get disabled again. I checked twice before call wifi calling was disabled. I tried on other GS20+ and was exactly the same situation. I rebooted phone, cleared cache nothing helps. I noticed that situation because I was downloading large files on my notebook when I was calling and call quality gets poor.