I flashed Arch ARM to my Pinephone eMMC and am trying to activate it with a Red Pocket T-Mobile card. It is showing 4G with a bar or two in the upper left corner. When I try to place a call, the calls app flashes something on the screen for a nano second such that I can't get a hint of what it shows. It then displays as a failed call in the log. I've tried it three different days from three different cities with the same result. I also tried a few texts but the app shows no information beyond logging the attempt and nothing is received.
Under the cellular settings > Access Points there is an LTE / t-mobile setting by default. I tried a custom addition with "cell data" "wholesale" in the fields like the Red Pocket email instructed. I've tried selecting both and it doesn't work either way.
Not sure where to look for help, I don't see much in these forums on the Pinephone, but the OS is a great improvement over the default Manjaro for other functions...