Phone apple direct demand to speak to a supervisor, advise of them of thus thread where thousands are reading up on the threads how to resolve the issue and new threads are posted daily
This problem has been caused by updating to 10.3.1 for a lot of people.
fiddling with your phone cellular settings, moving from 4g to 3G, resetting network settings, turning off automatic network selection might give some temporary signal, after 30 mins to 3 hours it will drop off, or if I try to change to 4g from 3G. I've changed sim, gone to the genius bar,to be told diagnistics show no fault, ive factory reinstalled through iTunes set up a new iCloud profile. Nothing works the issue is iOS 10.3.1 running on iPhone 6 on Vodafone U.K. My sure signal box at home Vodafone internet mobile signal also no longer works at all with my phone.
Apple need to provide some answers, either update or replace or hardware or release a fix in the next update.
Apple the silence on this issue has seriously effected my trust in your brand, I've heard nothing for 7 days from my so called personally assigned customer care supervisor. Dreadful service all around