I have discovered that when roaming in another country, it's currently not actually possible to remain manually connected to the same network carrier on the S22 Ultra.
I've just returned to the UK from a work trip in the United States and in previous years I've had no issues with using my Three UK sim in my old Galaxy S7 Edge wherever I have roamed, but this time using the exact same sim in my S22 Ultra (which works fine in the UK with 5G), when I arrived in the US I was not able to make any calls back to the UK, but was able to use data.
When I contacted Three UK they advised that I would need to change the S22 Ultra to use T-Mobile as it was connecting to AT&T by default, so I turned off the network carrier auto connect and manually selected T-Mobile. I was then able to make a call back to the UK, but after I finished the call, I tried to make another and it failed. It was then I saw that the phone had automatically switched back to using AT&T as the default carrier.
I have since worked out that despite turning off the option to automatically select the network carrier, after you are presented with the list of available carriers to manually select, as soon as you do this the phone will turn the aforementioned auto selection back on, so it's impossible to remain manually selected to one network carrier when you are roaming abroad.
To me this makes no sense whatsoever because there will be circumstances like the one I encountered where I need to be connected to the same carrier whilst roaming, especially one that is well established and not have to keep manually forcing the change every time I need to call my home country.
I did contact Samsung support live chat about this whilst out in the US and did as they suggested (reset network settings and also cleared the phone cache from the boot menu) but despite that, it still would not stay on the carrier that I manually selected in order to be able to make phone calls and just always default to an automatic mode no matter what I did.
It was suggested that because I was roaming abroad that this was the reason it will always revert to automated carrier selection, but my scenario is a good example to allow for the user to be able to have the availability to turn off this and choose a manually selected carrier whilst roaming and stay connected.
I assume that there is currently no work around and such a feature would require a software update (my S22 Ultra is up to date as I write this) so was wondering if there was some official way of requesting feature updates of this kind?
Any info / advice would be greatly appreciated!