Galaxy Note 10 - can't get VOLTE to work
But it also has no signal bars and an explicit "no signal" symbol (that crossed-out circle). That's what's confusing: those signal bars aren't for a voice service, they are the cellular connection strength, and it seems to be zero. Is it always like that, or was that screenshot just taken at a time when the signal was zero?
LTE = 4G data connection. It doesn't have a dedicated voice functionality, so originally 4G phones had to switch to 2G or 3G to make voice calls (they did this automatically, so you wouldn't notice unless you were watching the status bar). VoLTE = Voice over LTE, which is like Voice over IP (Voice over Internet Protocol, i.e. internet calling), a way of using a data connection to make a voice call. "WiFi calling" is another example of this idea. That's the way telecoms is going: all networks are just data networks.
So the addition of VoLTE allows 4G phones to make voice calls without switching to one of the older protocols, which in turn is what makes it possible for the networks to turn those off and re-use the spectrum for newer, higher-capacity systems (4G and 5G). So if for any reason you don't have VoLTE available, and can't use the older protocols, you could still have a data connection with no voice capability. You have turned on VoLTE calling, but it seems not to be working. The question is whether that's because your phone's implementation isn't compatible with your current network's (the worst case), because there's a configuration problem (in either your phone or for your account in their systems), or because there's a hardware fault (e.g. the bad SIM hypothsis), that's the tricky bit to work out: because if all anyone knows is that it's not working that doesn't rule anything out. All I can think of is to try the ones that can be tested (clearing your network settings, asking them to check your account is correctly configured, try asking for a new SIM) in whatever order is least inconvenient and hope one of them fixes it.
(I'm going to assume that greying-out of the "network operators" on an unlocked handset is a consequence of using that network's SIM, because I've no other explanation for it. So I'm afraid I'm still going to call your carrier a control freak
).
Seriously, the older I get the less comfort zone I try to hide in. I've reached a point where I'm not intimidated, afraid of failure, embarrassed, etc. Those are the things that I consider my comfort zone. As an old man, nobody expects a lot from me, and I can easily surpass that. Just don't ask me to do any public speaking. I suffer greatly from dyslexia and affluent speech I was not gifted with. I used to hide that fact in my comfort zone. Nowadays I just laugh at myself and go on down the road.
