I have used Pure Talk, an AT&T MVNO, since the beginning (well, my beginning in 2021). When I got the phone, Pure Talk was already 4G only. I purchased their SIM, did the settings all up right, and it worked immediately for standard text. After reading about why I was having the call issues, I went through the manual enabling 4G steps (which there is a program for now), but once I did that, the calls worked, and still work, pretty much fine. Every once in awhile it seems to forget it’s a phone and it needs to be restarted. But I know it’s working on 4G, not only because that’s all Pure Talk has, but also because I have it set to 4G only. Sometimes group and data messages are delayed/sketchy, but that seems to be a known problem.