iPhone SE, iOS 9.3.4
This phone was on Verizon for years, until a couple months ago when we switched to Xfinity Mobile as we are on WiFi at home like 99% of the time and it was 1/10 the price.
We have identical iPhone SEs and both appeared to switch over without incident, until a couple days ago when we were out of the house and discovered her phone could not receive or send Messages. On troubleshooting further, I discovered that her phone still thinks it's on Verizon as the carrier, but XM for the "Network" (I realize XM just leases network from Verizon, but my phone shows XM for both).
I've been escalated up to Tier 2 at XM, who also brought Verizon Networking into the discussion, but nobody could identify any problem with the phone, settings, etc. We went through the usual Network Settings Reset and All Settings Reset anyway, but no change. XM sent a replacement SIM card just in case that was the issue, but no change with that either.
On further troubleshooting this evening, I discovered that if I disable LTE data on her phone, then she is able to use 3G and can text and use data like normal. Of course it's very slow, but it works.
It looks to me like there is a carrier settings issue of some sort on her phone, although neither phone received a carrier update on switching SIM cards. There does not appear to be any way to manually "force" a carrier update either.
At this point I'm out of ideas other than a factory reset of the phone, but my wife absolutely does not want any change to her OS (we both have been burned badly in the past by Apple OS updates that we couldn't roll-back from) and I'm concerned that there may not be a way to update while retaining her OS. I've seen claims that it can be done, but I'm not totally convinced.
Is there any way to get this phone to recognize the LTE network and use it? Is it at all possible to manually enforce a carrier update? Does anyone have any other ideas on what might be happening here and how to address it?
