In which region are you?
Did you tried different providers?
I am in Nepal
Yes i did but not working.
I saw there were issues in some UK regions too after upgrading to A12. What is your OS build?
Just forget about it. You're not going to be able to do it. It's a problem with the Android 12 update that they still seem to haven't bothered fixing yet. I'm in Canada and I have the exact same problem since running the beta and now on to 11.C_16. That along with 5G and call waiting are just toast.
Have you tried looking in developer options? I'm pretty sure that to get 5g you have to us one of the NR network settings. Also check these settings in developer options. I don't have 5g so mine is greyed out. But turn on NR for calls.
Use this app to get to the network settings and use one that starts with NR to get 5g.
This is my Os version 11.c.16
Try the Samsung app i posted above. It will take you to the volte switch to see if it's turned on.
"Shot on OnePlus June: Colors" now available in Orbit!
by script, 2022-06-02