7.1 is also causing issues for people with hotspots.
Coming off a fresh installation of 7.1, I just discovered that my cellular data wasn't working (usually on wi-fi most of the time), and could only be restored if I downloaded a APN configuration file from the unlockit.co.nz site, or directly from my carrier (H2O).
I don't know if it's because I did a clean erase on my phone after installing 7.1, or if the new AT&T 16.0 carrier profile is at fault, but either way, I can confirm the SIM swap trick no longer works.
While attempting the swap, I did notice that the MMS domain was already set up, but pointing to mms.mobile.att.net instead. I did the swap twice--the first time, everything, including the APN domains, seemed to "stick," but I still couldn't get any data after restoring the SIM.
The second time, the APNs reverted themselves to "phone" after a brief pause and it was clear that it wouldn't work.
I'm not exactly sure how the settings and carrier profiles are supposed to interact, or affect UI, but under the previous 7.0.x setup, sans carrier configuration file, everything worked, even if it was still hard to tell which settings were being used, since there was no user accessible way to see, much less change them without the swap.
Can anyone explain why this stuff is hidden and can't be altered? Are they carrier rules, or Apple's rules?
I understand that older versions of iOS weren't as restrictive.
Living without MMS is no big deal, but I don't understand why some carriers allow it, and some don't.