Let's say you do root and unlock a Sprint HTC One to use with an AT&T Gophone sim. Any reason why you should still expect compatibility problems?
I rooted and unlocked the phone yesterday (or at least thought I did). Everything appears to be GSM-ready. Then when I go to Phone Info and set the preferred network type to GSM/WCDMA/LTE auto, or any non-CDMA setting, I get a steady zero bars. If I switch it to CDMA, I get a signal. I can't do anything with that signal obviously, nor do I want to, but the phone recognizes the network. The same thing happens whether I have the AT&T sim already in or if I change the settings with it out and pop it in after rebooting. Not sure if it matters, but APN have been changed to AT&T ones, too.
It's as if there's some setting that's still "locked" to CDMA/Sprint. Unlocked is unlocked though, even if I didn't unlock it through a code they furnish, right?
I've tried everything I can think of. I was thinking of posting a new thread but my problem sounds kinda similar to the OP's. Any help would be much appreciated.