T-Mobile users complain about iOS 10 carrier settings causing service blackouts [ux2]
A carrier settings update, associated with iOS 10, is causing some T-Mobile customers to lose their cellular connection in places where they should otherwise have a signal, according to complaints on Apple's support forums. [Updated with official T-Mobile response and promised Apple fix]

People encountering the issue are finding themselves completely offline until they reboot their phones or choose Reset Network Settings from the iOS Settings app. AppleInsider can confirm the existence of the glitch, which on Wednesday kept an editor's iPhone 6 offline in an area which normally has good reception. Rebooting the phone solved the situation.
Anecdotes suggest that the problem is related to how iPhones connect to T-Mobile's LTE network. It appears to be triggered by temporarily leaving LTE coverage, which can be troublesome if a person regularly passes through areas with poor or non-existent service, like elevators and parking garages.
The carrier update is suspected because the problem didn't manifest until this week, and is only affecting connections to one cellular network. Appropriately, people on T-Mobile's prepaid MetroPCS brand may also be impacted.
So far there's no indication of when the issue might be resolved, but T-Mobile will presumably push out another carrier update in the near future.
Update: T-Mobile CTO Neville Ray has taken to Twitter to elaborate on the issue, indicating that Apple is "working to fix an iOS 10 problem" within the next 48 hours. Until then, T-Mobile customers with an iPhone SE, 6, or 6 Plus are warned not to upgrade to iOS 10.
Update 2: Apple and T-Mobile have released a fix for the issue, meaning users are free to update to iOS 10 at their convenience.

People encountering the issue are finding themselves completely offline until they reboot their phones or choose Reset Network Settings from the iOS Settings app. AppleInsider can confirm the existence of the glitch, which on Wednesday kept an editor's iPhone 6 offline in an area which normally has good reception. Rebooting the phone solved the situation.
Anecdotes suggest that the problem is related to how iPhones connect to T-Mobile's LTE network. It appears to be triggered by temporarily leaving LTE coverage, which can be troublesome if a person regularly passes through areas with poor or non-existent service, like elevators and parking garages.
The carrier update is suspected because the problem didn't manifest until this week, and is only affecting connections to one cellular network. Appropriately, people on T-Mobile's prepaid MetroPCS brand may also be impacted.
So far there's no indication of when the issue might be resolved, but T-Mobile will presumably push out another carrier update in the near future.
Update: T-Mobile CTO Neville Ray has taken to Twitter to elaborate on the issue, indicating that Apple is "working to fix an iOS 10 problem" within the next 48 hours. Until then, T-Mobile customers with an iPhone SE, 6, or 6 Plus are warned not to upgrade to iOS 10.
Update 2: Apple and T-Mobile have released a fix for the issue, meaning users are free to update to iOS 10 at their convenience.
Comments
FWIW T-Mo is saying it's Apple who is working on the fix, rather than it being a T-Mobile created issue.
"T-Mobile is warning iPhone customers not to update to iOS 10, the latest software version, after several customers have reported ‘connectivity issues’ caused by the update...says it is working with Apple on a fix for the problems and expecting a permanent fix in the next day or two."
https://twitter.com/TMobile/status/776466023193030657FWIW rebooting is a temporary fix according to the thread.
I've never understood the rush to download on Day Zero....
The point I was trying to make to Mr. Entitled is that being responsible for the fault doesn't mean it doesn't affect others. I was trying to pop his isolation bubble that doesn't allow him to see the interconnectedness of the world.