I have a Samsung Galaxy Note 22 Ultra. Originally T-Mobile, but it was unlocked and is now on US Mobile Lite speed (using T-Mobile network). This problem is carrier-independent.
I live on a hill, and there is very limited cell signal indoor. The phone often switches between 4G and 5G all on its own even when set stationary on my desk in my home office. If I move around the house, it will sometimes hit cell dead spots, too. Even when the phone has cell signal, data transfer speed (speedtest) is measured in kbps, not mbps. Incoming calls seldom get through when the phone is on cell signal. Texting usually does, but sometimes with a lag of several minutes. Outgoing texts often get stuck and need to be resent. Basically, the cell signal is useless. I have tried other carriers, and they are even worse. Between the terrain on the hills, and the very strong building materials in my mansion, it is akin to a Faraday cage. I tried installing cell booster/repeater before, but it did not help, because the signal outside is too weak, especially during inclement weather. The booster actually made things worse.
Because of this, I have a 6-AP Unifi mesh Wifi system. I set Wifi calling preferences to "Wifi preferred". Obviously, I don't want cell to ever be the priority. Unfortunately, periodically, the phone shows the message "Wifi calling preferences have been optimized". And it resets the preference to "Cellular preferred". This happens every single day. How can I make the setting stick ?
The only workaround I can think of is to disable mobile data when I am at home, or put the phone in airplane mode, but that is not a great solution, as I may forget to turn it back on when I leave the house.
I found another thread about another user having the same issue on an S21 ultra. He solved it by disabling "switch to mobile data" under intelligent Wifi. Unfortunately, that setting was already off on mine. I just disabled all the other options under intelligent Wifi as well, but I doubt that will have the desired effect of locking the Wifi calling preferences.
I just did that. Used airplane mode and turned off Wifi calling. Called my cell phone from Google voice over Wifi. The call rang on my VoIP line, which uses voip.ms with a Grandstream HT802. Pretty neat ! I left a voice mail, and it ended up in my Google mailbox as an MP3 . Voice quality was awful in that MP3, though. Not sure if the call forwarding has something to do with it.
I also sent an SMS from Google voice to my cell. The SMS did not get forwarded to my VoIP line. That line does support SMS, and I normally get the texts sent to it in my Gmail, also. Once I turned off airplane mode, my smartphone received that text. Looks like the "text forwarding" feature is missing. It's not as big of a deal, though, as the texts should eventually get there with Wifi calling, even with a weak Wifi signal.
Wifi calling can work in the air under some circumstances. I'd love to describe what those are, but this forum keeps telling me I'm using a blocked word, without telling me which one it is, and I'm not going to make 100 edits to figure out what it is.
I remember when that started working. I find it odd that cellular features work even on WiFi when airplane mode is on. If I'm not mistaken, that wasn't always the case, but I could be remembering wrong. I remember the time that I noticed it working that way for the first time.
